Add thank-you system for follows, subscriptions, and raids

[thelabcat]

This goes a bit outside of Rumble Chat Actor's normal function, but I've seen people use such.

Proposed solution: A threading loop that looks at Cocorum and fires off the thank-you system. Maybe we should put this inside of the existing message sender loop. We could have the thank-you messages as string attributes that don't trigger when set to False. We could also make it so that if you set the attributes to True, it uses an internal default string, but setting them to a string uses that.