[css-color] CNS

[svgeesus]

https://drafts.csswg.org/css-color/#modifying-colors

Actually add the CNS thing.

[svgeesus]

On reflection, the issue (CNS named colors) is unrelated to the section it is in (color calculations) and thus the issue can be closed.

[xfq]

The inline issue also needs removing (or moving to another section), I think?

[tabatkins]

No, the function was originally called color() and was meant to be the host for CNS; it was then co-opted to also do color modifications. Now that it's named color-mod(), yeah, CNS doesn't belong there. If/when we add CNS, we'll do it in some new function.

[tabatkins]

(But yeah, the inline issue needs removal, and the grammar needs to be changed to define color-mod() rather than color().)