enable printer discovery

configuration.nix

@@ -102,6 +102,13 @@ in
   # Enable CUPS to print documents.
   services.printing.enable = true;
 
+  # enable auto discovery of printers
+  services.avahi = {
+    enable = true;
+    nssmdns4 = true;
+    openFirewall = true;
+};
+
   # Enable sound.
   # sound.enable = true;
   # hardware.pulseaudio.enable = true;