Add GitHub workflow to compile controller code in CI

[synergiator]

Using for example Arduino CLI, it's possible to validate code compilation online without having the actual board.

See also:

https://codeblog.dotsandbrackets.com/gitlab-ci-esp32-arduino/

[ElectricRCAircraftGuy]

@giorakor @nimrod46 , do you know how to do this? I think there may be an option under "Actions" at the top, for instance, to tell GitHub to auto-compile each PR that is submitted to make sure the Arduino code isn't broken. This is what you're saying, @synergiator , right?

[synergiator]

Yes. By this, we get also more clarity about required dependencies and their versions.

[labeneator]

This looks like a good place to start: https://github.com/adafruit/ci-arduino/blob/master/README.md