Create a CI workflow to run tests

[ddundo]

After expanding the test suite (#50) and creating a Docker image (#52), we could set up a CI workflow to run tests and require that all tests pass before merging PRs.

[btobers]

@ddundo Should this have been closed in PR #59? My understanding was that stating "Closes [Issue Ref]" would automatically close the linked issue, but this does not seem to have happened.

[ddundo]

It will automatically close once it gets merged into the master branch

[btobers]

Ah, got it. That's good to know.