use pyproject.toml ... modernize build

[tlambert03]

Pull request recommendations:
Here's the obnoxious repo update i was referring to :) while it was easier to do this all in one, I can break it up into smaller ones if you want. (and I will comment inline on things that might not be obvious)

or... if you're happy with things as they are, that's fine too :)

[codecov-commenter]

Codecov Report

Merging #51 (8c31339) into main (efee3a9) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #51   +/-   ##
=======================================
  Coverage   88.88%   88.88%           
=======================================
  Files           3        3           
  Lines         189      189           
=======================================
  Hits          168      168           
  Misses         21       21           

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[evamaxfield]

omg. I will look at this over the weekend but i truly can't thank you enough. actively learning all the new things.

[evamaxfield]

90% of this makes sense to me! A few questions and comments. I really appreciate you doing this ❤️

[evamaxfield]

Assuming lint passes. Looks good to me! Thanks again!