Should the custom ::highlight pseudos be mentioned among the other highlight pseudos defined at https://drafts.csswg.org/css-pseudo-4/#highlight-selectors?

Custom highlights are different from the other pseudos in that they have their own standalone spec, but it seems like there should be at least a note about them in [css-pseudo-4] where the other highlight pseudos are covered.

I attempted to integrate them here: #6754. Not sure if that is the right approach.

cc @sanketj @frivoal