Draft: Add Dangerbot

What does this MR do?

Add Dangerbot via https://gitlab.com/explore/catalog/gitlab-org/components/danger-review

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for this project, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Security reports checked/validated by reviewer