Add CONTRIBUTING.md

[hborawski]

• Copy PR template from player
• Add CONTRIBUTING.md
• Update README with link to CONTRIBUTING and add some content from player README

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (5a0014b) 55.52% compared to head (a094306) 55.52%.

❗ Current head a094306 differs from pull request most recent head e15815f. Consider uploading reports for the commit e15815f to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #52   +/-   ##
=======================================
  Coverage   55.52%   55.52%           
=======================================
  Files          63       63           
  Lines        3238     3238           
  Branches      965      965           
=======================================
  Hits         1798     1798           
  Misses       1103     1103           
  Partials      337      337           

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