[web-animations-1] Export play state for animations

[jakearchibald]

In the view transitions spec we want to write prose about the current play state of an animation.

It feels like this prose is right:

If animation's play state is paused…

If that's correct, I propose:

• Make play state for="animation" and exported.
• Create a <dfn export>play state</dfn>.
• Make the various play states for="play state" and exported. Change their link text to things like "paused" rather than "paused play state", since they'd already be properly namespaced.

[jakearchibald]

Ohh, thanks for making that change so quickly. Fwiw, I'm happy if you throw it to me to make the change.