[feature request] resolve room ID to alias

hey o/

it would be nice if mjolnir could also resolve the room alias for a given room ID.
Right now it works only alias -> ID

If this is more work then supposed, feel free to close the request :)

thanks & greetings,
Shin

No files, tests, or entry points are named. Start by locating the existing alias-to-room-ID resolution in the TypeScript code and identify the Matrix lookup it uses; done means a room ID can be resolved to its room alias without breaking the existing reverse direction.

Written by the indexing model from the issue text.