Add support for Python 3.10

[joshuadavidthomas]

• switches workflow job matrix from rc1 to 3.10 proper, with passing tests
• updates trove classifiers

[codecov]

Codecov Report

Merging #1511 (c5227f4) into main (3b26935) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1511   +/-   ##
=======================================
  Coverage   85.73%   85.73%           
=======================================
  Files          35       35           
  Lines        1893     1893           
  Branches      276      276           
=======================================
  Hits         1623     1623           
  Misses        190      190           
  Partials       80       80           

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[joshuadavidthomas]

Requesting a review because this is my first jazzband repo I have been given the big green merge button and I would like another set of eyes before merging.

[joshuadavidthomas]

Thanks @auvipy!