style: added lua annotations to init methods

lua/tokyonight/init.lua

@@ -1,8 +1,10 @@
 local util = require("tokyonight.util")
 local theme = require("tokyonight.theme")
+local config = require("tokyonight.config")
 
 local M = {}
 
+---@param opts Config|nil
 function M.load(opts)
   if opts then
     require("tokyonight.config").extend(opts)
@@ -10,6 +12,9 @@ function M.load(opts)
   util.load(theme.setup())
 end
 
+M.setup = config.setup
+
+-- keep for backward compatibility
 M.colorscheme = M.load
 
 return M