Make a bot to automate point releases and avoid the "contact a maintainer" steps

[seadanda]

Ideally there would be a bot command so you could call /cmd point-release or whatever in a comment on a PR made against the x.y.z branch, the bot would create branch x.y.b, rebase the PR to x.y.b then trigger the release process from release-* branch when it sees the usual changelog changes when the branch is merged.
Probably would need to know which release is on chain and only allow +1s to avoid lots of branches being made.

Originally posted by @seadanda in #536 (comment)