Django 4.0 and Python 3.10 support

[vchrisb]

This does add Django 4.0 and python 3.10 to matrix testing.

[codecov]

Codecov Report

Merging #283 (f79cb64) into master (2d9c7dc) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #283   +/-   ##
=======================================
  Coverage   97.40%   97.40%           
=======================================
  Files           5        5           
  Lines         270      270           
=======================================
  Hits          263      263           
  Misses          7        7           

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[codingjoe]

Added two commits, again we don't need to support EOL versions.

[codingjoe]

Thanks @vchrisb, really appreciate the help here!