Add support for emitting github action annotations for soundness checks

[dimitribouniol]

It would be awesome if soundness checks emitted code-level annotations via workflow commands in PRs. Last I used them, it was as simple as echo-ing a special syntax to indicate file, line, and column information.

Namely, this could be useful for:

• header checks
• format/lint checks
• acceptable language checks

(It would be extra cool if this also worked for failing tests, but that might be a tad more involved).