Idea so skins can use a random frame upon an action

[The-Grace-God]

I know this probably could fit into #341 but i felt like it would fit better here. Another idea i had was the ability for the skin to set not only animations but also random frames what i mean by this is if something happens like the player hitting an object the skin can use a randomly pulled sprite instead of either in series with one another or as an animation. Best example i have to explain this is the hit effect in muse dash for the miniboss.