Animation Worklet Draft Spec for Tokyo F2F

Last meeting, we presented a high level design for AnimationWorklet and
promised to come back with a spec. AnimationWorklet is a new primitive for
creating high performance procedural animations on the web. We will be
presenting our first draft of the AnimationWorklet spec
<https://wicg.github.io/animation-worklet/> at the Houdini F2F in Tokyo.
We've been working on an implementation in blink <https://crbug.com/430155> and
will be soliciting feedback from developers in the coming months and would
appreciate your feedback.

Thanks,
Rob