Update README.md

[jonathanBieler]

The readme build status badge is broken (still links to travis), this replaces it with the github workflow badge.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 26.52%. Comparing base (bb65b7c) to head (d072092). Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #556   +/-   ##
=======================================
  Coverage   26.52%   26.52%           
=======================================
  Files          20       20           
  Lines        1248     1248           
=======================================
  Hits          331      331           
  Misses        917      917           

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