Support for 32 colors
pico-8 allows up to 32 colors through an [undocumented hack](https://pico-8.fandom.com/wiki/Palette#128..143:_Undocumented_extra_colors) that ended up being officially approved by the developer.

It'd be nice if pyxel can also support 32 colors, maybe optionally through the `.pyxpal` palette file.