Python 3.11 support

[seifertm]

• Updates Tox and CI to run tests on Python 3.11
• Adjust changelog and Trove classifiers

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.09%. Comparing base (a31916d) to head (d3221cf).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #370   +/-   ##
=======================================
  Coverage   93.09%   93.09%           
=======================================
  Files           3        3           
  Lines         275      275           
  Branches       41       41           
=======================================
  Hits          256      256           
  Misses         12       12           
  Partials        7        7           

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