text: Title: Add type hints for mypy
  Body: ### Description
  
  I would like to propose adding type hints to cartopy so that mypy can be used with the project.
  
  #### Code to reproduce
  
  Using the following code (adapted from the [global map](https://scitools.org.uk/cartopy/docs/latest/gallery/lines_and_polygons/global_map.html) tutorial):
  ```python
  import matplotlib.pyplot as plt
  import cartopy.crs as ccrs
  
  
  fig = plt.figure(figsize=(10, 5))
  ax = fig.add_subplot(1, 1, 1, projection=ccrs.Robinson())
  
  ax.set_global()
  ax.stock_img()
  ax.coastlines()
  
  ax.plot(-0.08, 51.53, 'o', transform=ccrs.PlateCarree())
  ax.plot([-0.08, 132], [51.53, 43.17], transform=ccrs.PlateCarree())
  ax.plot([-0.08, 132], [51.53, 43.17], transform=ccrs.Geodetic())
  
  plt.show()
  ```
  If you run:
  ```console
  > mypy --strict plot.py
  ```
  you'll see several errors.
  
  #### Traceback
  
  ```
  test.py:2: error: Skipping analyzing "cartopy.crs": module is installed, but missing library stubs or py.typed marker  [import-untyped]
  test.py:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
  test.py:2: error: Skipping analyzing "cartopy": module is installed, but missing library stubs or py.typed marker  [import-untyped]
  test.py:8: error: "Axes" has no attribute "set_global"  [attr-defined]
  test.py:9: error: "Axes" has no attribute "stock_img"  [attr-defined]
  test.py:10: error: "Axes" has no attribute "coastlines"  [attr-defined]
  Found 5 errors in 1 file (checked 1 source file)
  ```
  
  <details>
   <summary>Full environment definition</summary>
  
  <!-- fill in the following information as appropriate -->
  
  ### Operating system
  
  macOS and Linux
  
  ### Cartopy version
  
  0.22.0
  
  ### conda list
  
  N/A
  
  ### pip list
  
  ```
  Package                       Version
  ----------------------------- -----------
  absl-py                       1.4.0
  aenum                         3.1.12
  affine                        2.1.0
  aiohttp                       3.8.4
  aiosignal                     1.2.0
  alabaster                     0.7.13
  altgraph                      0.17.2
  antlr4-python3-runtime        4.9.3
  anyio                         4.0.0
  appdirs                       1.4.4
  appnope                       0.1.3
  argon2-cffi                   21.3.0
  argon2-cffi-bindings          21.2.0
  arrow                         1.2.3
  asttokens                     2.4.0
  astunparse                    1.6.3
  async-lru                     1.0.3
  async-timeout                 4.0.2
  attrs                         23.1.0
  Babel                         2.12.1
  backcall                      0.2.0
  beautifulsoup4                4.12.2
  black                         23.11.0
  bleach                        6.0.0
  Bottleneck                    1.3.7
  build                         1.0.3
  cachetools                    5.2.0
  Cartopy                       0.22.0
  certifi                       2023.5.7
  cffi                          1.15.1
  cftime                        1.0.3.4
  charset-normalizer            3.1.0
  click                         8.1.3
  click-plugins                 1.1.1
  cligj                         0.7.2
  cmocean                       3.0.3
  colorama                      0.4.6
  comm                          0.1.3
  contourpy                     1.0.7
  coverage                      7.2.6
  cycler                        0.11.0
  debugpy                       1.6.7
  decorator                     5.1.1
  defusedxml                    0.7.1
  docstring-parser              0.15
  docutils                      0.18.1
  editables                     0.3
  efficientnet-pytorch          0.7.1
  einops                        0.7.0
  et-xmlfile                    1.0.1
  executing                     1.2.0
  fastjsonschema                2.16.3
  filelock                      3.12.4
  Fiona                         1.9.4
  flake8                        6.1.0
  fonttools                     4.39.4
  fqdn                          1.5.1
  frozenlist                    1.3.1
  fsspec                        2023.1.0
  future                        0.18.2
  GDAL                          3.8.0
  geocube                       0.3.2
  geopandas                     0.11.1
  gevent                        23.7.0
  google-auth                   2.20.0
  google-auth-oauthlib          0.5.2
  greenlet                      2.0.2
  grpcio                        1.52.0
  h5py                          3.8.0
  hatch-jupyter-builder         0.8.3
  hatchling                     1.18.0
  huggingface-hub               0.14.1
  hydra-core                    1.3.1
  idna                          3.4
  imageio                       2.30.0
  imagesize                     1.4.1
  importlib-metadata            6.6.0
  importlib-resources           5.12.0
  iniconfig                     2.0.0
  ipykernel                     6.23.1
  ipython                       8.14.0
  ipywidgets                    8.0.2
  isoduration                   20.11.0
  isort                         5.12.0
  jaraco.classes                3.2.3
  jedi                          0.18.2
  Jinja2                        3.0.3
  joblib                        1.2.0
  json5                         0.9.14
  jsonargparse                  4.25.0
  jsonpointer                   2.0
  jsonschema                    4.17.3
  jupyter_client                8.2.0
  jupyter_core                  5.3.0
  jupyter-events                0.6.3
  jupyter-lsp                   2.2.0
  jupyter_server                2.6.0
  jupyter_server_terminals      0.4.4
  jupyterlab                    4.0.1
  jupyterlab-pygments           0.2.2
  jupyterlab_server             2.22.1
  jupyterlab-widgets            3.0.3
  keyring                       23.13.1
  kiwisolver                    1.4.4
  kornia                        0.7.0
  laspy                         2.2.0
  lazy_loader                   0.1
  lightly                       1.4.18
  lightly-utils                 0.0.2
  lightning                     2.1.2
  lightning-utilities           0.8.0
  macholib                      1.15.2
  Markdown                      3.4.1
  markdown-it-py                3.0.0
  MarkupSafe                    2.1.3
  matplotlib                    3.8.2
  matplotlib-inline             0.1.6
  mccabe                        0.7.0
  mdurl                         0.1.2
  mistune                       2.0.5
  more-itertools                9.1.0
  mpmath                        1.2.1
  multidict                     6.0.4
  munch                         2.5.0
  mypy                          1.7.0
  mypy-extensions               1.0.0
  nbclient                      0.6.7
  nbconvert                     7.4.0
  nbformat                      5.8.0
  nbmake                        1.4.3
  nbsphinx                      0.8.8
  nest-asyncio                  1.5.6
  netCDF4                       1.6.2
  networkx                      3.1
  notebook_shim                 0.2.3
  numexpr                       2.8.4
  numpy                         1.26.2
  oauthlib                      3.2.1
  odc-geo                       0.1.2
  omegaconf                     2.3.0
  openpyxl                      3.1.2
  overrides                     7.3.1
  packaging                     23.1
  pandas                        2.1.3
  pandocfilters                 1.5.0
  parso                         0.8.3
  pathspec                      0.11.1
  pexpect                       4.8.0
  pickleshare                   0.7.5
  Pillow                        10.0.0
  pip                           21.2.4
  pkginfo                       1.9.6
  planetary-computer            0.4.9
  platformdirs                  3.10.0
  pluggy                        1.0.0
  pooch                         1.7.0
  pretrainedmodels              0.7.4
  prometheus-client             0.17.0
  prompt-toolkit                3.0.38
  protobuf                      3.20.3
  psutil                        5.9.5
  ptyprocess                    0.7.0
  pure-eval                     0.2.2
  pyasn1                        0.4.8
  pyasn1-modules                0.2.8
  pybind11                      2.11.0
  pycocotools                   2.0.6
  pycodestyle                   2.11.0
  pycparser                     2.21
  pydantic                      1.10.9
  pydocstyle                    6.2.1
  pyflakes                      3.1.0
  pygeos                        0.14
  Pygments                      2.16.1
  pyparsing                     3.0.9
  pyproj                        3.2.1
  pyproject_hooks               1.0.0
  pyrsistent                    0.19.3
  pyshp                         2.1.0
  pystac                        1.4.0
  pystac-client                 0.5.1
  pytest                        7.3.2
  pytest-cov                    4.0.0
  python-dateutil               2.8.2
  python-dotenv                 0.19.2
  python-json-logger            2.0.7
  pytorch-lightning             2.0.0
  pytorch-sphinx-theme          0.0.24
  pytz                          2023.3
  pyupgrade                     3.3.1
  pyvista                       0.42.3
  PyWavelets                    1.4.1
  PyYAML                        6.0
  pyzmq                         25.0.2
  radiant-mlhub                 0.3.1
  rarfile                       4.1
  rasterio                      1.3.8
  readme-renderer               37.3
  requests                      2.31.0
  requests-oauthlib             1.3.1
  requests-toolbelt             1.0.0
  rfc3339-validator             0.1.4
  rfc3986                       2.0.0
  rfc3986-validator             0.1.1
  rich                          13.4.2
  rioxarray                     0.4.1.post0
  rsa                           4.9
  Rtree                         1.1.0
  safetensors                   0.3.1
  scikit-image                  0.20.0
  scikit-learn                  1.3.2
  scipy                         1.11.4
  scooby                        0.5.7
  segmentation-models-pytorch   0.3.3
  Send2Trash                    1.8.0
  setuptools                    63.4.3
  Shapely                       1.8.1
  six                           1.16.0
  sniffio                       1.3.0
  snowballstemmer               2.2.0
  snuggs                        1.4.1
  soupsieve                     2.4.1
  Sphinx                        5.3.0
  sphinx-copybutton             0.2.12
  sphinx_design                 0.4.1
  sphinx-rtd-theme              1.2.2
  sphinxcontrib-applehelp       1.0.4
  sphinxcontrib-devhelp         1.0.2
  sphinxcontrib-htmlhelp        2.0.1
  sphinxcontrib-jquery          4.1
  sphinxcontrib-jsmath          1.0.1
  sphinxcontrib-programoutput   0.15
  sphinxcontrib-qthelp          1.0.3
  sphinxcontrib-serializinghtml 1.1.9
  stack-data                    0.6.2
  sympy                         1.11.1
  tensorboard                   2.14.1
  tensorboard-data-server       0.7.0
  terminado                     0.17.1
  threadpoolctl                 3.1.0
  tifffile                      2023.8.30
  timm                          0.9.2
  tinycss2                      1.2.1
  tokenize-rt                   4.2.1
  torch                         2.1.1
  torchmetrics                  1.2.0
  torchvision                   0.16.1
  tornado                       6.3.3
  tqdm                          4.66.1
  traitlets                     5.9.0
  trove-classifiers             2023.8.7
  twine                         4.0.2
  typeshed-client               2.1.0
  typing_extensions             4.8.0
  tzdata                        2023.3
  uri-template                  1.2.0
  urllib3                       1.26.12
  vermin                        1.5.2
  wcwidth                       0.2.7
  webcolors                     1.11.1
  webencodings                  0.5.1
  websocket-client              1.6.3
  Werkzeug                      3.0.0
  wheel                         0.41.2
  widgetsnbextension            4.0.3
  xarray                        2023.7.0
  yarl                          1.9.2
  zipfile-deflate64             0.2.0
  zipp                          3.17.0
  zope.event                    4.6
  zope.interface                5.4.0
  ```
  
  </details>
  