add classes hook for customizations

[atmonshi]

• the main container: fi-preset-color-picker
• for items: fi-preset-color-picker-item
• for active/selected item: fi-preset-color-picker-item-active

[atmonshi]

not sure if it should be documented but I added either way

[awcodes]

Can you change these to maybe 'pcp-' instead of 'fi-'?

I don't want people to think they are filament hooks.

😀

[atmonshi]

fair, from dev pov, my eye used to scan fi- for classes in the source 😅

[awcodes]

sweet, thanks.