Add CI enforcement for no `CHANGELOG.md` changes

[szokeasaurusrex]

Manual changes to CHANGELOG.md should only be allowed in PRs starting with meta(changelog):. Changing the changelog in another change should not be allowed. If someone tries to manually edit the changelog in an unrelated change, a GitHub comment should be posted on the PR to inform the user that changelogs should be generated automatically, and that edits to the changelog need to be done via a meta(changelog): PR

[linear]

CLI-263