Add documentation

[vicky5124]

There's currently no documentation available for anything rillrate-py, stubs files mentioned in #2 will help a bit with this, but full documentation should be written. Thankfully, this is quite easy to do, as pdoc (https://pdoc.dev/) supports building documentation from linked library files, but doc comments and function signatures will still need to be added to every function, method and "class" defined in the source.

https://github.com/vicky5124/lavasnek_rs/ Lavasnek has followed this approach with very happy results; you can check out the source code, to see how documentation is written, and also the macros used for function signatures. pdoc -o docs .env/lib/python3.9/site-packages/lavasnek_rs is used to build the documentation, after maturin develop has been run.

https://github.com/mitmproxy/pdoc/issues/239 Note that .pyi files are not yet supported by pdoc, so type values should be written in the documentation, as they won't show up in the documentation otherwise.