gdk: Add support for some color conversions
Add private apis for converting between srgb, hwb, oklab and oklch.
See https://bottosson.github.io/posts/oklab/ and https://www.w3.org/TR/css-color-4/.
Add private apis for converting between srgb, hwb, oklab and oklch.
See https://bottosson.github.io/posts/oklab/ and https://www.w3.org/TR/css-color-4/.