Sphinx API docs are empty

The `python_sphinx` target for `ninja` builds docs for `aqt` Python bindings only and they're mostly empty.

I'd like to add docstrings to the `pylib` and `aqt` classes and functions for easier-to-read auto-generated API docs generation using existing `autoapi` and `Sphinx` while adding `sphinx.ext.napoleon` and `sphinx.ext.autodoc.typehints` extensions.

The existing single-quote annotations on some functions help when working in the IDE but Sphinx doesn't generate docs from them. Also, not all functions or classes in the python bindings have annotations.

I already started working on this and have a couple functions "doc-stringed" in the `decks.py` file of pylib.
Before I get too far, how would you prefer to break up docstring commits so that edits are manageable to review?

Start with the `python_sphinx` target and the existing `autoapi` and Sphinx configuration, then review the partially docstringed `pylib` `decks.py` file. Check how the proposed `sphinx.ext.napoleon` and `sphinx.ext.autodoc.typehints` extensions affect the `pylib` and `aqt` API output; done means the scope and commit breakdown are agreed and the generated docs are no longer mostly empty.

Written by the indexing model from the issue text.