[css-animationworklet] Animator section order depends on concepts and definitions which haven't been introduced.

[flackr]

Currently, the Animator section starts with a description of the WorkletAnimation objects you can create, and then describes the animator definition, and then how to register it.

I think it would flow more naturally to first have a concepts section describing the animator definition concept, then how an animator definition is registered, and finally the animator can be described as an animation instance (of type WorkletAnimation) which computes the animationeffect time via its animator definition's animate function.