allow inverting the role-reaction toggle

[JuicyJuuce]

On our server we take a minimalist approach and prefer that users have the least number of roles as necessary. As such, I auto-assign users a new user role and restrict them to only being able to read one channel until they react to the "read first" message at the bottom. Currently the only way to do this with YAGPDB is to require them to click it twice, which new discord users sometimes stumble on and end up clicking it 3 times or 5 times or some other odd number of times and never get past it.

This could be avoided if there was a setting that allowed the role-reaction toggle to be inverted. As in: if they click the emoji once they lose the role.