Add support for Oklab Color Standard

[Gh0stD3x]

Feature Description

Brief:
The OKLab color space offers perceptual uniformity, improving color accuracy and consistency in visual applications. Implementing OKLab in the Slint GUI framework would enhance color manipulation, interpolation, and overall user experience.

Technical Benefits:

• Perceptual Uniformity: Ensures consistent color perception, crucial for applications requiring precise color representation.
• Improved Color Accuracy: Facilitates high-fidelity color reproduction, essential for design and visual data
• Enhanced Interpolation: Allows for smoother color transitions and animations, resulting in a more appealing
• Alignment with Modern Standards: Meets contemporary design trends favoring vibrant and accurate color
• Future-Proofing: Positions Slint to adapt to evolving color management technologies.

A good explaination of the oklab color standard can be found here.

Would also be good as a first issue for someone else, as hsv and rgb are already implemented.

Product Impact

Its not very critical, but would greatly enhance Quality of Life, building apps in slint. Would also be great for creating palletes with nicelooking color transitions.

[ogoffart]

I guess we could have a Colors.oklab(...) following the CSS spec: https://developer.mozilla.org/en-US/docs/Web/CSS/color_value/oklab

[ogoffart]

Akthough it seems that this is not a simple function and will need a @oklab(...) syntax understood by the parser. (similar to the @linear-gradiant thing)