Animation sequence

@mattgperry Hi! I've just found this library because i'm working on a small vanilla js project and i have to say that's very impressive! :) I was looking into the documentation, also inside old Popmotion pose, and i've noticed that some methods are not available anymore in the latest Popmotion (v9.x); i was wondering, is there a way to easily replicate those behaviors? For example for staggered or timeline animations.

Thanks :)