Add conversions to and from Oklab and LCHOklab

[nealmckee]

Currently failing as the type doesn’t exist yet.

To and from XYZ, everything else through XYZ.

I’m using the original specifications provided here: https://bottosson.github.io/posts/oklab/

This is my first contribution to Julia, or any software package for that matter, so any help would be greatly appreciated. For example, should I also add this to the docs?

See also JuliaGraphics/ColorTypes.jl#271

[Artoria2e5]

LCHOklab is known as Oklch now after CSS4.

[jariji]

It's reported that

unfortunately Colors.jl has been without maintainers for a couple of years; kimikage stepped away, and timholy and johnnychen are too busy elsewhere… It needs someone with the time,authority, and expertise to take up the challenge. But hopefully one day your PRs will be merged!

[timholy]

Yes. Not quite sure I understand, are you volunteering @jariji ?

[timholy]

This needs tests.

[jariji]

@timholy I'm not volunteering for this, I just noticed this PR and that OP said

This is my first contribution to Julia, or any software package for that matter, so any help would be greatly appreciated.

so I figured I could let OP know what's going on, so they'd understand why they haven't heard anything.

[kimikage]

PR #533 was merged.