refactor(waybar): register owned modules

configs/nixos/registry/window-icon.nix

@@ -10,9 +10,9 @@
       };
 
       icon = lib.mkOption {
-        description = "Sets the Nerd Font codepoint shown for matching windows.";
+        description = "Sets the icon shown for matching windows.";
         type = lib.types.str;
-        example = "f269";
+        example = "";
       };
     };
   };