make module imports like recommended by snowfall

modules/template.nix

@@ -18,6 +18,8 @@ systems, # An attribute map of your defined hosts.
 # All other arguments come from the module system.
 config, ... }:
 
+with lib;
+
 let cfg = config.modules.X;
 in {
   options.modules.X = { enable = mkOption { default = false; }; };