Document the individual modules better

[JustAnotherArchivist]

The modules are currently not documented very well, especially their limitations (e.g. Twitter not discovering retweets).

[ppival]

I'd love to help with this!

[JustAnotherArchivist]

That would be greatly appreciated!

Preferably, this part would be directly in the code as docstrings since that makes it much less likely to forget about updating the docs on code changes. It would also automatically serve as a partial documentation of the API (#7). I'll have to think a bit about how to make it easily accessible, but that's down the line anyway.

[reynoldsnlp]

Numpy docstrings are a great human- and machine- readable format for docstrings: https://numpydoc.readthedocs.io/en/latest/format.html

[JustAnotherArchivist]

Unfortunately, numpydoc doesn't support proper type hints: numpy/numpydoc#196

The ideal solution would be something like https://github.com/agronholm/sphinx-autodoc-typehints/issues/149 I think. I haven't done much research on this though (yet).