Group#onChildInputUp

This Signal is dispatched whenever a child of this Group emits an onInputUp signal as a result
of having been interacted with by a Pointer. You can bind functions to this Signal instead of to
every child Sprite.

This Signal is sent 3 arguments: A reference to the Sprite that triggered the signal,
a reference to the Pointer that caused it, and a boolean value isOver that tells you if the Pointer
is still over the Sprite or not.