[css-animations-1] Use range notation for <keyframe-selector> as a percentage #7140
Description
<keyframe-selector> is defined as follows:
<keyframe-selector> = from | to | <percentage>Values less than 0% or higher than 100% are invalid and cause their
<keyframe-block>to be ignored.
I think it can be explicitly defined with the CSS bracketed range notation.
<keyframe-selector> = from | to | <percentage [0,100]>