breaking: standardize palette

vimbones and nordbones follow standard palatte table:

require("nordbones.palette").dark instead of "derived"

lua/vimbones/palette.lua

@@ -2,8 +2,12 @@ local util = require "zenbones.util"
 local lush = require "lush"
 local hsluv = lush.hsluv
 
-return util.palette_extend({
+local M = {}
+
+M.light = util.palette_extend({
 	bg = hsluv(85.9, 27, 94),
 	fg = hsluv(0, 0, 22),
 	vim = hsluv(131.8, 92, 51),
 }, "light")
+
+return M