Move to pyproject.toml

[gordonwatts]

Move to using pyproject and hatch rather than old setup.py

Fixes #238

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.02%. Comparing base (9021caa) to head (d1b9375).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #256   +/-   ##
=======================================
  Coverage   95.02%   95.02%           
=======================================
  Files          35       35           
  Lines        2009     2009           
  Branches      221      221           
=======================================
  Hits         1909     1909           
  Misses         64       64           
  Partials       36       36           

Flag	Coverage Δ
unittests	95.02% <ø> (ø)

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