[CI] Run Dangerbot

Summary

In other groupdistribution project, we run Dangerbot to perform various checks during merge request pipelines.

We should enable Dangerbot for Operator CI as well, especially to validate existence of commit trailers for changelog generation (#44 (closed)).

Acceptance criteria

• Dangerbot configuration is added to the codebase
• Dangerbot configuration includes validation for existence of commit trailers (Charts reference)
• Dangerbot is configured to run in CI

References

• Charts Dangerfile configurations
• Charts changelog config
• Charts CI config to run Dangerbot