text: Title: Use the path .gpteng for storing logs etc per default
  Body: ### Details
  
  Change the workflow of gpt-engineer to be like so:
  
  - Always set `memory` and `archive` folders paths to be to the .gpteng folder (which will create it per default if it doesn't exist)
  - Always set `workspace` and `input` folder paths to be directly in the `project path`
  
  
  <details open>
  <summary>Checklist</summary>
  
  - [X] `gpt_engineer/db.py`
  > • Modify the `__init__` method of the DB class to set the default paths for the `memory` and `archive` folders to be in the `.gpteng` folder.
  > • Modify the `__init__` method of the DB class to set the default paths for the `workspace` and `input` folders to be in the `project path`.
  > • Modify the `__init__` method of the DB class to create the `.gpteng` folder if it does not exist.
  
  - [X] `tests/test_db.py`
  > • Update any tests related to the default paths of the `memory`, `archive`, `workspace`, and `input` folders to reflect the changes in the DB class's `__init__` method.
  > • Add a test to verify that the `.gpteng` folder is created if it does not exist.
  
  - [X] `docs/intro/db_class.md`
  > • Document the changes to the default paths of the `memory`, `archive`, `workspace`, and `input` folders.
  > • Document the creation of the `.gpteng` folder if it does not exist.
  
  </details>
  