refactor lualine resolution

- create util to determine theme just by the name
- read config from colorschemes.json

lua/lualine/themes/zenbones.lua

@@ -1 +1 @@
-return require("lualine.themes.zenbones_" .. vim.opt.background:get())
+return require("zenbones.util").get_lualine_theme("zenbones")