SIMD colorspace conversion

Description

We should be able to use SIMD to compute color space conversion operations, making them faster.

This should give us at least 1a 3x CPU improvement, but proper benchmarks should be made.

added enhacement label

assigned to @joamag

mentioned in merge request !45 (merged)

It seems there are massive improvements for M1 chip but not so much on x86 machines.

to be able to use SIMD one must use nightly rust and --features simd

mentioned in commit 5ad29997

closed with merge request !45 (merged)