Add chatops commands to FF Rollout template

What does this MR do?

Add ChatOps commands to the rollout template.

Why? When managing feature flags I often find myself copying and it would be useful to have them directly in the rollout issue. They are pretty stable, so this is unlikely to get outdated at this point.

Screenshots

N/A

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• [-] Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Related to #237862 (closed)