Consider support for interpolate expressions in Oklab color space

Motivation

I was recently investigating Oklab for a personal project (after seeing now the default for gradients in Photoshop: https://twitter.com/bjornornorn/status/1453069681082896394) and while I am not a color theorist, this article claims it has some perceptual improvements over CIELAB, especially in terms of blue hue. https://raphlinus.github.io/color/2021/01/18/oklab-critique.html

I wonder if what the effort is to support an interpolate-oklab expression to go with interpolate-lab, and if that effort is worth having more perceptually accurate color blending.

Design Alternatives

I am unaware of the complexity of adding interpolate-oklab, so we could just do nothing and have access to the CIELAB color space.

Design

https://docs.mapbox.com/mapbox-gl-js/style-spec/expressions/#interpolate-lab

We already have an interpolate-lab expression, so from my perspective copying that seems fine, but if there's any drawbacks to that design we should rethink for an interpolate-oklab expression I'd assume that's ok as well.

Mock-Up

["interpolate-oklab", ["linear"], ["get", "step"], 0, "red", 1, "blue"]

Concepts

Implementation

Start by reviewing the existing interpolate-lab expression and the linked style-spec expression documentation to identify the relevant parsing, evaluation, and test entry points. Compare the proposed interpolate-oklab syntax with interpolate-lab, investigate the color-conversion and edge-case requirements, and define completion as the expression working consistently across the Mapbox GL ecosystem with documentation and tests.