Add support for Python 3.10

[thangleiter]

Should work out of the box, just need to add tests.

[codecov]

Codecov Report

Merging #75 (f93e105) into master (3df1c6c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #75   +/-   ##
=======================================
  Coverage   97.28%   97.28%           
=======================================
  Files           9        9           
  Lines        2247     2247           
  Branches      512      512           
=======================================
  Hits         2186     2186           
  Misses         28       28           
  Partials       33       33           

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