feat(css): add missing css color-mix() function

[skyclouds2001]

Description

the css color-mix() function has been supported in all major platform for more than one year per bcd

Motivation

Additional details

https://developer.mozilla.org/en-US/docs/Web/CSS/color_value/color-mix
https://drafts.csswg.org/css-color-5/#funcdef-color-mix

Related issues and pull requests

report in csstree/validator#29

[skyclouds2001]

full test log in chromium:

CSS.supports('color', 'color-mix(in oklab, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in srgb, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in srgb-linear, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in display-p3, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in a98-rgb, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in prophoto-rgb, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in rec2020, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in lab, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in oklab, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in xyz, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in xyz-d50, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in xyz-d65, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in hsl, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in hwb, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in lch, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in oklch, #a71e14 0%, white)')
true
CSS.supports('color', 'color-mix(in lch shorter hue, var(--base) 0%, var(--mixin) )')
true
CSS.supports('color', 'color-mix(in lch longer hue, var(--base) 0%, var(--mixin) )')
true
CSS.supports('color', 'color-mix(in lch increasing hue, var(--base) 0%, var(--mixin) )')
true
CSS.supports('color', 'color-mix(in lch decreasing hue, var(--base) 0%, var(--mixin) )')
true
CSS.supports('color', 'color-mix(in --swop5c, var(--base) 0%, var(--mixin) )')
true
CSS.supports('color', 'color-mix(in --my-color-profile, var(--base) 0%, var(--mixin) )')
true

Note

Though the <custom-color-space> syntax of <color-interpolation-method> syntax, which should be defined using non-supported @color-profile feature. Test shows that this syntax is supported in color-mix(), so added this at present.