Should we have a !mjolnir mute command?

[ghost]

I know that the same can be achieved using the !mjolnir powerlevel command but having a dedicated mute command is easier, this would also be necessary if we use membership state in the future to track mutes instead of power levels (MSC3909).

May help with fixing #62

[FSG-Cat]

If mjolnir implements MSC3907 and MSC3908 it would be able to be considered as fixing #62 without having to solve MSC3909. MSC3909 is still a draft because i cant finish it currently due to that the Authorisation rules writing is beyond my skills.

Edit: I should also point out that Powerlevels dont actually map to Policy Lists unlike mutes under MSC3907