Fix/add more palettes for extended classes

Imported from legacy Flarum.
Original author: WhiteKitty (Flarum #561)

For every extended class, there are only around 8 maximum palettes which look decent, but every color after that is an eyesore. looks like mixed paint or smth. makes customizing extended class characters extremely difficult because the colors are limited.

Imported from legacy Flarum.
Original author: Muh (Flarum #1)

Their turn for fixed palettes will come, just needs some more time