Use declarative metadata and declare support for Python 3.10

[hugovk]

Forgot the 3.10 Trove classifier in #44.

[codecov]

Codecov Report

Merging #45 (c9ab724) into main (4869140) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #45   +/-   ##
=======================================
  Coverage   55.91%   55.91%           
=======================================
  Files           4        4           
  Lines         431      431           
=======================================
  Hits          241      241           
  Misses        190      190           

Flag	Coverage Δ
GHA_Ubuntu	55.91% <ø> (ø)
GHA_macOS	55.91% <ø> (ø)

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