!mjolnir rooms should put the returned room list in a code block

[Twi1ightSparkle]

Is your feature request related to a problem? Please describe.
When you have lots of protected rooms, the list returned from !mjolnir rooms takes up a lot of space and can be cumbersome to scroll through in the timeline.

Describe the solution you'd like
Mjolnir should put list list returned from !mjolnir rooms into a code block as they are collapsed by default in Element.

Describe alternatives you've considered
None comes to mind

Additional context
None