Add "specifying a color profile: the `@color-profile` at-rule"

[Schweinepriester]

https://drafts.csswg.org/css-color/#at-profile

Moved @color-profile and device-cmyk to level 5 per CSSWG resolution

=> https://drafts.csswg.org/css-color-5/#at-profile

The @color-profile rule defines and names a color profile which can later be used in the color() function to specify a color.

Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1352760

[GPHemsley]

Defined by CSS Color Module Level 5 (#5405):
https://www.w3.org/TR/css-color-5/#at-profile

Likely to be covered by MDN data in the future:
https://developer.mozilla.org/en-US/docs/Web/CSS/@color-profile