handleCollisionEnd method
Calls the two colliding hitboxes once when two hitboxes have stopped colliding. They are called with instances of each other, so that they can determine what hitbox (and what ShapeHitbox.hitboxParent that they have stopped colliding with.
Implementation
@override
void handleCollisionEnd(ShapeHitbox hitboxA, ShapeHitbox hitboxB) {
hitboxA.onCollisionEnd(hitboxB);
hitboxB.onCollisionEnd(hitboxA);
}