text: Title: Notebook/script templates generated by "ploomber scaffold" should contain a cell with the autoreload magic
  Body: If `ploomber scaffold` finds a `pipeline.yaml` if checks all `tasks[*].sources` and creates files for all tasks whose source is missing. e.g., 
  
  ```yaml
  tasks:
      - source: scripts/some-script.py
        product: output.ipynb
  ```
  
  If `scripts/some-script.py` does not exist, it creates one.
  
  The created script contains a basic structure for users to get started. It'd be useful to add the following as the first cell:
  
  ```python
  # uncomment the next to lines to enable auto-reloading
  # for more info: https://ipython.readthedocs.io/en/stable/config/extensions/autoreload.html
  # %load_ext autoreload
  # %autoreload 2
  ```
  
  This is a pretty handy but relatively unknown feature of IPython that auto-reloads modified code.
  
  Documentation: https://ipython.readthedocs.io/en/stable/config/extensions/autoreload.html
  
  
  File to modify: https://github.com/ploomber/ploomber/blob/ac915ea998f4da0177204f2189f8f608f3404fc6/src/ploomber/resources/ploomber_add/task.py
  
  
  This is the line that triggers file creation when executing "ploomber scaffold": https://github.com/ploomber/ploomber/blob/ac915ea998f4da0177204f2189f8f608f3404fc6/src/ploomber/cli/cli.py#L67
  
  Add tests here: https://github.com/ploomber/ploomber/blob/master/tests/cli/test_scaffold.py
  
  
  
  
  