Add a github actions reporter: adds a step summary table + annotations for minitest

[jmarrec]

Styling could be improved, more metrics from the rubocop + OpenStudio Style could be added. But this is good proof of concept, and I needed it for another project.

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Example run (this is on a private repo...):

Step summary on workflow run

Annotations on workflow run

Annotations on diffs

[jmarrec]

@kflemin @DavidGoldwasser If someone could merge that'd be great. The jenkins workflow is completely bricked, and I don't have the juice necessary to merge without the status check.