Add Github actions workflow to build on PR/push.

[TaplistIOTeam]

Action is based on reference implementation: https://docs.platformio.org/en/latest/integration/ci/github-actions.html

The only local change of significance in the action is that we've disabled the platformio asset caching step, given that we currently have some un-pinned dependencies. See discussion in https://github.com/thorrak/tiltbridge/pull/185

[TaplistIOTeam]

You can see an example of this action's execution in my trial branch:

https://github.com/TaplistIO/tiltbridge/runs/2327360783?check_suite_focus=true

It currently fails for reasons that are under discussion in #185.

I don't think there would be negative consequence to merging this change, even with the build broken:

• Github actions execution minutes are free for open source projects
• The action's execution/failure does not intrinsically block PR merges (although you could later configure the repository to do so).

[thorrak]

Am I correct in my reading that all this does at the moment is a test build (to ensure that a merge doesn't break anything)?

[TaplistIOTeam]

Yes, that's correct. You'll basically get a green check if all targets are built successfully, and a failure otherwise. Along with the build logs, of course.

I think as a baseline, it could be a convenient way to check that incoming PRs build and don't break anything, in a hermetic build environment. Of course there are fancier things you could do subsequently; e.g., automatically create github releases & the accompanying binaries. (I am by no means an expert but have some modest experience here in other projects, happy to help further.)

(Sorry if you saw this comment twice, bouncing between work/personal accounts!)