[feature request] List rooms where a give user is inside

Hey all 👋🏻

This is a "nice-to-have" from my side.

Would it be possible to give mjolnir the possibility to list the rooms where a given user is inside?

Many thanks =)
Shin

The issue names no files, tests, or command entry point. Start by finding how Mjolnir currently lists rooms or accepts a user identifier, then determine the Matrix membership information available for that user. Done means a user can request and receive the rooms where that user is present.

Written by the indexing model from the issue text.