[Feature Request] Add customizable theme and color settings.

[WindsorMacmillan]

Is your feature request related to a problem? Please describe. I expect more theme configurations of custom segments instead of only 3 levels (good, medium and poor). And also bossbar color theme. Something like:

color-scheme { #When value (in %) reaches the level below, use that color. performance-level= [25,50,75,100] performance-color= [green,yellow,gold,dark_purple] bossbar-level= [15,30,45,60,75,90] bossbar-color= [aqua,green,yellow,gold,red,light_purple] text=gray text-secondary=white }