Feature/migrate to GitHub actions

[chewiebug]

migrating from travis to github actions.

Should cover

• pull request workflow
• develop snapshot build (including upload to Sonatype snapshot repository and sourceforge releases)

Does not cover

• master release builds (including upload to Sonatype release repository)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.48%. Comparing base (eb2676f) to head (0723892).
⚠️ Report is 12 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #286      +/-   ##
=============================================
- Coverage      70.61%   70.48%   -0.13%     
- Complexity      1553     1567      +14     
=============================================
  Files            146      146              
  Lines           8769     8820      +51     
  Branches        1419     1437      +18     
=============================================
+ Hits            6192     6217      +25     
- Misses          1984     2009      +25     
- Partials         593      594       +1     

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