Typing notifications can be sent in a channel without `SendMessage` perms

[TaiAurori]

If Revolt.js is used to send a typing indicator in a channel which the current user has no SendMessage permission in, the typing indicator still goes through to other users despite the fact this seems like it shouldn't be possible. Ideally, typing notifications should also be blocked with absence of SendMessage.

[insertish]

This can now be checked using the state information.