OKLch color picker with Orthogonal Chroma, in addition to OkHSL

Summary:

#7733 (closed) led to the addition of a perceptual colour picker to Inkscape. This employs OkHSL, but OkHSL is not orthogonal in chroma.

I propose that another OKLch colour picker be added to Inkscape, in addition to existing OkHSL one.