doc: adding config line for home-manager (#1680)

- related to #1679

README.md

@@ -222,7 +222,10 @@ programs.neovim = {
     {
       plugin = pkgs.vimPlugins.avante-nvim;
       type = "lua";
-      config = ''require("avante").setup()'' # or builtins.readFile ./plugins/avante.lua;
+      config = ''
+              require("avante_lib").load()
+              require("avante").setup()
+      '' # or builtins.readFile ./plugins/avante.lua;
     }
   ];
 };