Add gradle GitHub action

[brericha]

Runs gradle build and gradle test on any merge or push into master.

Not ready to merge yet, gotta see if there's a way to test that the action works first.

[brericha]

When I finally figure this out I'll do another branch so we don't clutter the commit lot with all these attempts

[brericha]

It appears to be working now but the build currently fails because lint is catching a problem, see issue #195

[dektar]

This is stellar. LG after we fix the build error. I can pick that up as I just did another back pressed handling, or you are welcome to it (please assign yourself if you do it so we don't step on each other).

I'd just suggest we talk with Nick to make sure there's no limit or at least no small limit to how many github actions we can perform. I'm not sure if/how we pay for GitHub.

[nickoneill]

We have a non-profit business account on GitHub so I would not worry about action limits (I think the free tier is already fine for just a handful of people making PRs anyway). As for commits, you can still use this branch @brericha, just pick "Squash and merge" rather than "Merge" when done.

[dektar]

Thank you so much for working on this! It'll be great to have.