New rgb() function syntax for completion

[AioiLight]

Currently rgb() function completions are comma-separated values, but this is the old syntax, which is a legacy format that does not allow setting the alpha channel.

Also, to go along with this, issue (microsoft/vscode#139840) needs to be fixed, which changes to comma-separated syntax when changing colors in the color picker.

[kingma-sbw]

See https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Colors/Color_values for a complete description.

Category	Modern syntax examples	What it represents	Why it’s “modern”
Space-separated RGB	rgb(255 0 0 / 0.5)	Red, green, blue + optional alpha	Replaces rgba(); unified, cleaner syntax
Space-separated HSL	hsl(0 100% 50% / 0.5)	Hue, saturation, lightness + alpha	Replaces hsla(); consistent with RGB format
HWB	hwb(0 0% 0% / 0.5)	Hue, whiteness, blackness	Simpler mental model than HSL
Lab	lab(54% 80 67 / 0.5)	Perceptual lightness + color axes	Device-independent, closer to human vision
LCH	lch(54% 106 40 / 0.5)	Lightness, chroma, hue	More intuitive than Lab
OKLab	oklab(0.6 0.1 0.1 / 0.5)	Improved perceptual model	Better uniformity than Lab
OKLCH	oklch(0.6 0.15 40 / 0.5)	Lightness, chroma, hue (modern model)	Preferred for design systems
color() function	color(display-p3 1 0 0 / 0.5)	Explicit color spaces (e.g. P3)	Enables wide-gamut colors
color-mix()	color-mix(in oklch, red 50%, blue)	Mixes colors in a chosen space	Powerful dynamic color composition
relative color syntax	rgb(from red r g b / 50%)	Derives colors from another	Enables programmatic color adjustments
light-dark()	light-dark(black, white)	Picks color based on theme	Built-in dark mode support
currentColor	currentColor	Uses element’s computed color	Still fully modern and widely used

the last column shows that this was generated with AI