A simple class for registering keyup/keydown events and identifying if a
key is currently being pressed.
An object whose keys are key codes from the
Keys dictionary and
values are boolean flags indicating if the corresponding key is
currently being pressed.
A callback triggered after the "keydown" event. Receives the "event"
object as a parameter.
A callback triggered after the "keyup" event. Receives the "event"
object as a parameter.