nixos/eternal-terminal: add firewall information

(#71917)

nixos/modules/services/networking/eternal-terminal.nix

@@ -23,6 +23,8 @@ in
         type = types.int;
         description = ''
           The port the server should listen on. Will use the server's default (2022) if not specified.
+
+          Make sure to open this port in the firewall if necessary.
         '';
       };
 
@@ -86,4 +88,8 @@ in
       };
     };
   };
+
+  meta = {
+    maintainers = with lib.maintainers; [ pingiun ];
+  };
 }