Consider using postcss-selector-parser to implement the :matches(…) selector

[ExE-Boss]

postcss-selector-parser has been made with the goal of improving the handling of css selectors in postcss plugins by making sure to avoid outputting broken selectors (see #7, #14, #16).

[jonathantneal]

I am doing this in the next release. I am only struggling with the expansion of selectors.