Add GitHub Actions Output Formatter

[jtaylor100]

Implements #282

Based it on the ConsoleOutputFormatter but left out any printing of the inheritance dependencies since I don't understand it. Perhaps it could be done later.

Tested using https://github.com/jtaylor100/random-reviews (basic Symfony project).

See https://github.com/jtaylor100/random-reviews/actions/runs/118086775 for how the output looks.

Any feedback appreciated.

[smoench]

@jtaylor100 Thank you @jtaylor100! Looks good to me.

Is there a way to support multilines for the output? We need to adapt inheritance dependencies as it might be hard to find the path / cause of such violation.

[smoench]

Thank you @jtaylor100!