The red-circle emoji represents "at capacity"

What does this MR do?

This MR documents a behaviour I've seen maintainers adopt in recent months. If a maintainer has set their GitLab status to 🔴, this means we have too many MRs to review and we will reject any attempt to pass them more.

This is something to encourage, rather than discourage, as it helps us to meet our "2 business days" SLO and short-cuts a request-response cycle. However, if we're doing it, we should document it.

An example of when it's useful: !17439 (comment 268123286)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)