DOC: implement basic docs

[stsievert]

What does this PR implement?
It provides basic API documentation. This PR does not provide a getting started guide, examples or tutorials.

I think focusing on documentation will help simplify the API.

References issues/PRs
This closes #46.

[codecov-commenter]

Codecov Report

Merging #58 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #58   +/-   ##
=======================================
  Coverage   99.51%   99.51%           
=======================================
  Files           3        3           
  Lines         413      413           
=======================================
  Hits          411      411           
  Misses          2        2           

Impacted Files	Coverage Δ
scikeras/wrappers.py	99.70% <ø> (ø)

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[adriangb]

Thank you for this PR. I need to figure out how to make readthedocs play well with poetry...

[adriangb]

This is looking good now. I added a couple of goodies to like linking to GH, borrowed from Skorch/sklearn. Since this does not modify any of the existing docs or functionality, I'm going to merge as-is and we can improve these docs as we go.