Serialize a simple selector seems incomplete

[annevk]

In particular https://drafts.csswg.org/cssom/#serialize-a-simple-selector doesn't seem to acknowledge that the prefix can also be * and might need to be serialized at times (and not as \*). Also, it's a tad unclear that step 3 and 4 are mutually exclusive.

(This is applicable to both elements and attributes.)

[AtkinsSJ]

It's also missing handling for some pseudo-classes:

• :dir()
• :host and :host()
• :where() and :is()
• [of S]? support for :nth-child() and :nth-last-child()
• :nth-col() and :nth-last-col()