TEST: Test using GitHub workflows for CI

[dpogue]

Platforms affected

macOS, Windows, Linux?

Motivation and Context

This potentially allows us to move away from TravisCI and Appveyor and consolidate all of our CI builds on a single system, which will hopefully be fast to run.

Description

Set up a GitHub Action that runs the tests automatically on Windows, macOS, and Linux (Ubuntu) when a PR is opened. Currently it's testing with node 10 and 12 (as per our plan to drop node 6 and 8).

Testing

Should get a bunch of green checkmarks from GitHub...

To Be Addressed

• Reporting code coverage (there are some issues with codecov in GH actions needing a token. Coveralls looks like a workable alternative)
• Ideally run eslint once as its own step, and report any concerns back inline in the file diff. GH actions isn't quite able to do this nicely yet, but it's on the way.

[codecov-io]

Codecov Report

Merging #95 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #95   +/-   ##
=======================================
  Coverage   88.17%   88.17%           
=======================================
  Files          20       20           
  Lines        1759     1759           
  Branches      361      361           
=======================================
  Hits         1551     1551           
  Misses        208      208

---

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[erisu]

Other than the comments, I think we might be able to start planning to merge this in.

It would be nice to also get some coverage service working but I am not entirely sure coveralls will work either.

Is the token something that must be kept as a secret or could it be added to a yaml file?

Additional Reference:
Since I mentioned cordova-eslint's usage in a few areas, here is a link to the file.
https://github.com/apache/cordova-eslint/blob/master/.github/workflows/nodejs.yml

[erisu]

LGTM 👍

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.28%. Comparing base (291158c) to head (addb22c).
Report is 87 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #95   +/-   ##
=======================================
  Coverage   86.28%   86.28%           
=======================================
  Files          21       21           
  Lines        1560     1560           
=======================================
  Hits         1346     1346           
  Misses        214      214           

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