Gazebo: Add no_time_sync and no_lockstep options

- Add extra fields to JSON message.

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>

Author: srmainwaring

src/ArduPilotPlugin.cc

@@ -2000,6 +2000,14 @@ void gz::sim::systems::ArduPilotPlugin::CreateStateJSON(
       writer.EndObject();
     }
 
+    // Set no time sync
+    writer.Key("no_time_sync");
+    writer.Bool(true);
+
+    // Set no lockstep
+    writer.Key("no_lockstep");
+    writer.Bool(false);
+
     writer.EndObject();
 
     // get JSON