Fires when a modifier key is pressed or released.
Signature:
("key", state)
Arguments:
key- The name of the key that you pressed. Possible values are LSHIFT, RSHIFT, LCTRL, RCTRL, LALT, and RALT. (string)state- The state the key has entered. 1 means that the the key has been pressed. 0 means that the key has been released. (number)