Add Sphinx build config and more user docs, docstrings, type annotations, etc.

[JWCook]

Closes #69, updates #49

Let me know if you have any questions about how Sphinx works or about the extensions used. These tools have a bit of a learning curve, but once everything is set up you can mostly forget about it.

Besides the changes to build and publish docs, I've added and edited quite a bit of documentation, mainly in the Readme. A diff is not very useful here, so see the rendered doc instead: https://github.com/JWCook/PyrateLimiter/blob/docs/README.md

I've tried to organize it roughly in order of what I think a new user will want to know first:

• Basic info
  • Feature summary
  • Install instructions
  • A couple basic examples that can be easily copy-pasted
• More detailed/advanced info
  • Details on handling rate limit exceptions or delays
  • Details on other usage options (decorator, contextmanager, async, etc.)
  • Bucket backends
• Contributing guide (now on a separate page)

Please look that over and let me know what you think.

[codecov]

Codecov Report

Merging #70 (7d19a10) into master (0632081) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
+ Coverage   98.15%   98.18%   +0.02%     
==========================================
  Files           8        8              
  Lines         380      386       +6     
  Branches       34       33       -1     
==========================================
+ Hits          373      379       +6     
  Misses          4        4              
  Partials        3        3              

Impacted Files	Coverage Δ
pyrate_limiter/bucket.py	94.16% <100.00%> (ø)
pyrate_limiter/exceptions.py	100.00% <100.00%> (ø)
pyrate_limiter/limit_context_decorator.py	100.00% <100.00%> (ø)
pyrate_limiter/limiter.py	100.00% <100.00%> (ø)
pyrate_limiter/request_rate.py	100.00% <100.00%> (ø)
pyrate_limiter/sqlite_bucket.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0632081...7d19a10. Read the comment docs.

[vutran1710]

@JWCook Looks great to me

[JWCook]

@vutran1710 Okay, I think this is ready to go. I did a manual build from my branch so you can see a preview here: https://pyrate-limiter.readthedocs.io

Were you able to add that webhook to trigger doc builds? Details here. Once that's done, it will rebuild the docs every time you push to the master branch. Or it can be built only for git tags or other conditions, if you prefer.