Extend ColorSpace support

[jossmac]

I'm doing some work related to design tokens. The primitives from RAC are terrific, but support only three color spaces: "rgb", "hsl", and "hsb".

Would you consider, or is there intent to, add support for other common spaces e.g. "lab", "lch"?

[snowystinger]

We don't currently have plans to extend built-in support, however, we had talked about allowing people to extend what we have so people can bring their own color spaces. We'd accept an RFC on the topic if you're interested.

[devongovett]

I had looked into it a while ago. The hard part isn't so much adding the color spaces, it's designing a UI that makes sense for editing in those spaces. For example lab is not a rectangular space so mapping it onto a ColorArea doesn't make much sense. Something like described in this article might work, but that limits the gamut to sRGB. We could potentially support larger gamuts like P3, but with gamut-less spaces like oklch, it is more challenging.