docs: Clean up small issues in docs

[AndreasAlbertQC]

Motivation

Polishing.

Changes

• Added intersphinx support so we can link to other projects properly.
• Wherever applicable, I fixed up class/method/function references to render as hyperlinks
• Added the napoleon extension so our doc strings are parsed more robustly. This resolves small styling problems with lists of arguments in docstrings, as well as with Exceptions in docstrings
• Removed outdated docstring references to the mypy plugin

Note: you cannot currently link to polars.DataFrame and polars.LazyFrame, which seems to be a problem in the polars doc build, not on our end. You can verify that these classes do not appear in the structured output sphinx uses: pixi run -e docs python -m sphinx.ext.intersphinx https://docs.pola.rs/py-polars/html/objects.inv

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (4c2bac7) to head (c82f0a3).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #180   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           50        50           
  Lines         2897      2904    +7     
=========================================
+ Hits          2897      2904    +7     

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[borchero]

Thanks a lot! Regarding polishing documentation: can we also get rid of the double backticks in the docstrings? 😄