GH action to test for proper formatting

[jdebacker]

This PR adds a second GH action to test for proper code formatting. This repo is using the black code formatter with 79 character lines.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5efcf9f) 86.84% compared to head (7f618d9) 85.71%.
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
- Coverage   86.84%   85.71%   -1.14%     
==========================================
  Files           3        4       +1     
  Lines         403      406       +3     
==========================================
- Hits          350      348       -2     
- Misses         53       58       +5     

Flag	Coverage Δ
unittests	85.71% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.