let push rules be published as state events?

could be cool for a room admin to be able to define custom keywords which should push everyone in a given room - e.g. `@team`. it's not necessarily abusive, given room admins can say @`room` already

No files, tests, or entry points are mentioned. Start by reviewing the Matrix specification's push rules and state events, then define the protocol changes needed for room-admin custom keywords and document the resulting behavior.

Written by the indexing model from the issue text.