Review CSS Animation Worklet API

[michael-n-cooper]

Review CSS Animation Worklet API.

[michael-n-cooper]

This relates to #12 and it's possible the issues are all there, but the API should be reviewed in light of it.

[digilou]

Per APA discussion, might be resolved, thanks to the introduction of Media Queries 5 'prefers-reduced-motion'. Will be discussed at TPAC.

[digilou]

Concerns for animation accessibility have been quelled by Media Queries 5 progress.