Allow anchor-size(…) in arbitrary values

[RobinMalfait]

This PR fixes an issue where using anchor-size in arbitrary values resulted in the incorrect css.

Input: w-[calc(anchor-size(width)+8px)]
Output:

.w-\[calc\(anchor-size\(width\)\+8px\)\] {
  width: calc(anchor - size(width) + 8px);
}

This PR fixes that, by generating the correct CSS:

.w-\[calc\(anchor-size\(width\)\+8px\)\] {
  width: calc(anchor-size(width) + 8px);
}