Decorate pull request with mutants that aren't killed

**Is your feature request related to a problem? Please describe.**
There is no clear qualtiy gate for a mutation test where there is an mutant that survives the tests. So now I can merge my PR without fixing the mutants.

**Describe the solution you'd like**
It would be very cool if the action can decorate a PR so that I am forced to fix my surviving mutants before I can merge my PR.

