Allow animating the player's costumes through the API, if able

[Meowlala]

Being able to animate player costumes through code would greatly simply the creation of charged items and recreation of similar base game features, like Breath of Life's costume.

Naturally because of how the costume system works, it's sometimes impossible to animate the player's costume and make a visible charge animation. The base game gets around this by making the player flash colors instead, which would also be nice to have easy access to.

[im-tem]

Note: this functionality is technically present with items like Mega Mush (bigisaac.anm2) which has Transform and TransformBack animations, so all we need are some bindings to allow using those costume animations in Lua.