Update/review v3 docs

[JWCook]

Follow-up from https://github.com/vutran1710/PyrateLimiter/pull/111#pullrequestreview-1590143981

Tasks:

• [ ] Add parameter documentation for all public classes and functions
• [ ] Update to Sphinx v7 if possible, and verify other doc dependencies/extensions are still working
• [ ] Verify structure and content in HTML docs:
  • [ ] Table of contents and sidebar page outlines
  • [ ] Auto-generated module docs (via sphinx-apidoc)
• [ ] Verify formatting in HTML docs:
  • [ ] Docs generated from docstrings
  • [ ] Docs generated from markdown

[JWCook]

I haven't been able to get to this yet, but I still plan to as soon as I have the time.

[andrew-cybsafe]

Given the substantial changes from 2.x to 3.x, I'd suggest that a migration guide would be very helpful. e.g.

• how do I implement @limiter.ratelimit("...", delay=True) in v3.
• RequestRate class has renamed to Rate