Move config documentation into docstrings

[boolean5]

We could port some of our configuration documentation from Configuration.md to docstrings in config.py.

An idea would be to keep some parts of Configuration.md, such as the introductory part and the Browser profile support section, and point to the documentation that's autogenerated from the docstrings where needed.

[Ayushsunny]

Hello @boolean5 I would like to work on this issue. can you guide me for this?

[vringar]

Hey,
to resolve this issue I'd like you to do the following things:

1. Move the documentation from Configuration.md into the respective docstring of the attributes here
   E.g. for data_directory currently in Configuration.md it says "The directory into which screenshots and page dumps will be saved" so you'd write under https://github.com/mozilla/OpenWPM/blob/889b54d4295e1ad5c0da24c29a3b0ed746da33ba/openwpm/config.py#L119-L122

"""The directory into which screenshots and page dumps will be saved"""

2. Figure if it's possible to link from the Configuration.md to the generated class documentation and if it isn't convert Configuration.md into Configuration.rst at which point you should be able to link to the generated class documentation.