feat: event when an object is stomped on or headbutted (reflected forms of onGround and onHeadbutt)

[dragoncoder047]

There's events for when an object hits the floor (onGround) and hits the ceiling (onHeadbutt). Where are the equivalents for the thing that was hit (i.e. onStomped and onHeadbutted)?

I'm making a button object that will react when it a falling object (which may or may not be the player) lands on it from above, and for the event handler that makes the stomped-on button react to the stomp, it doesn't make much sense to attach it to the thing that's falling (by tag or otherwise)...

[lajbel]

let me know if it looks good