Add Pseudo-elements support

[Awilum]

Please add Pseudo-elements support.

A CSS pseudo-element is a keyword added to a selector that lets you style a specific part of the selected element(s). For example, ::first-line can be used to change the font of the first line of a paragraph.

For more detailed information about which CSS properties can be used with each of these, please refer to the MDN documentation.

[Awilum]

hmm, seems it's already covered by SCOPES

https://asmcss.com/docs/1.x/scopes.html