Draft: Add help command to issues

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR adds support for using the @gitlab-bot help command in issue notes. To date we have instructed community contributors in our Get Help documentation to use this command in both MRs and issues. But it only functions in MRs. This would ping a random MR coach into the issue to help out / redirect a contributor who uses the command.

Off the back of a conversation when updating this Get Help documentation here: gitlab-org/gitlab!157838 (comment 1974352087)

Current processor for the command in MRs: https://gitlab.com/gitlab-org/quality/triage-ops/-/blob/master/triage/processor/community/command_mr_help.rb

Expected impact & dry-runs

These are strongly recommended to assist reviewers and reduce the time to merge your change.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/tree/master/doc/scheduled#testing-policies-with-a-dry-run on how to perform dry-runs for new policies.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/blob/master/doc/reactive/best_practices.md#use-the-sandbox-to-test-new-processors on how to make sure a new processor can be tested.

Action items

• If adding environment variables for reactive processors, update config/triage-web.yaml and .gitlab/ci/triage-web.yml
• (If applicable) Add documentation to the handbook pages for Triage Operations =>
• (If applicable) Identify the affected groups and how to communicate to them:
  • /cc @person_or_group =>
  • Relevant Slack channels =>
  • Engineering week-in-review