Add support for user typing event

[pcktm]

Hi, do you plan do add support for handling the typing indicator?
That would come in really, really handy.

[ptrcnull]

As far as I'm concerned, Facebook doesn't send us the typing indicator on /t_ms channel (the one we're currently subscribing to), so we'll have to find out more about it.
But yeah, it sounds like a great feature to have.

[ptrcnull]

btw @pcktm, could you join our Discord or DM me (Bjornskjald#4972)?