What problem does this solve or what need does it fill?

We don't need clone ActiveAnimation struct repackage to myself's struct

A description of why this particular feature should be added.
If update function public,we can easy to do once animation or myself's animation function

What solution would you like?

Let update function public, and add a system update all ActiveAnimation.
But I not sure what question happend after public function.

What alternative(s) have you considered?

Actually,this change will make ActiveAnimation didn't only work by BevyAnimationSystem but also allow we do complex system whatevr is not animation

Other solutions to solve and/or work around the problem presented.
If ActiveAnimation update function cause unsafe or another din't able public, We can repackage ActiveAnimation for update function still private.

Additional context

I make a easy OnceAnimationSystem,it will work one or more I can't sure.
If animation into resource,it will be waster memory.