Show color decorators for oklab and oklch colors

[thecrypticace]

Now we can display color decorators for colors using lab, lch, oklab, and oklch.

Given that these are wide-gamut color spaces the behaviors here are a bit different:

• Color decorators display the closest sRGB approximation of the color
• Color equivalent hex values only appear when the color is displayable within the sRGB color space
• Color presentations / pickers are not supported. VSCode (and the language server protocol in general) does not yet support wide-gamut colors so allowing modifications and interactions in this way would be lossy.

Fixes #887