Add the Msh color space

The Msh color space, [introduced by Kenneth Moreland](https://www.kennethmoreland.com/color-maps/ColorMapsExpanded.pdf), was designed to facilitate diverging color maps that avoid Mach banding at the central white or black region. This issue typically arises from abrupt luminance transitions. The `coolwarm` color map, which was created with Msh, highlights this advantage when compared to the `vlag` color map: `vlag`: <img width="512" height="48" alt="image" src="https://github.com/user-attachments/assets/c98bab66-d947-4098-bc7b-2e71cd7f9d60" /> `coolwarm`: <img width="512" height="48" alt="image" src="https://github.com/user-attachments/assets/1a243c09-1740-49c9-ab17-c451bd61f2c1" />