Move Builds from TravisCI to GitHub Actions

[timnolte]

Is your feature request related to a problem? Please describe.
Due to the limit of TravisCI credits now we've exhausted our credits for at least the rest of the month.

Describe the solution you'd like
Move builds to GitHub Actions in order to at least provide another means to perform validation/check builds.

Describe alternatives you've considered

• Staying with TravisCI and just managing the credits limit was the hope. Having burned through the credits due to trying to get the new build matrix working there doesn't seem to be another choice. I'm not going to pay for these builds.
• Just validation everything locally and continue to use a local environment for WordPress plugin deployments.