Replace Travis with GitHub Actions

[jgwerner]

• Removes Travis-CI configuration files
• Adds GitHub Action workflow yamls to lint, test and build/push docker images

[codecov[bot]]

Codecov Report

Merging #628 (1d1f94a) into main (03770b3) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #628   +/-   ##
=======================================
  Coverage   69.44%   69.44%           
=======================================
  Files          10       10           
  Lines         769      769           
=======================================
  Hits          534      534           
  Misses        235      235           

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