Define keyframes

Generates keyframes, method to create keyframe animations in CSS

let fadeIn = %keyframe(`
  0% {
    opacity: 0;
  }
 
  100% {
    opacity: 1;
  }
`)
 
module Component = %styled.div(`
  animation-name: $(fadeIn);
  width: 100px;
  height: 100px;
`)

let fadeIn = %keyframe(`
  0% {
    opacity: 0;
  }
 
  100% {
    opacity: 1;
  }
`)
 
module Component = %styled.div(`
  animation-name: $(fadeIn);
  width: 100px;
  height: 100px;
`)

Braces are optional. %keyframe({ ... })%keyframe({ ... }) and %keyframe(...)%keyframe(...) are the same.
The keyframe name is defined outside of the CSS.
The type of the keyframe is string, but hidden in an opaque type.