Scoped styles break @keyframes with percentages

[Gyanreyer]

It looks like the scoped prefix class is getting applied to each keyframe percent, which ends up breaking the animation so that it doesn't work. Oddly, I don't think I've observed this issue when using from or to.

Example:
This:

<style webc:scoped>
  @keyframes my-anim {
    0% { opacity: 0; }
    100% {  opacity: 1; }
  }
</style>

Results in:

<style>
  @keyframes my-anim {
    .prefix-class 0% { opacity: 0; }
    .prefix-class 100% { opacity: 1; }
  }
</style>

[zachleat]

Successfully reproduced.

[zachleat]

Related upstream csstree/csstree#178

[zachleat]

Shipping with the next release, thank you!