Only send skybrowser topic message if data changed

Maybe a little ugly to check the jsonString, but it does the job for now. Later we should probably make a nicer implementation

modules/server/include/topics/skybrowsertopic.h

@@ -46,6 +46,8 @@ private:
     int _targetDataCallbackHandle = UnsetOnChangeHandle;
     bool _isDone = false;
     std::chrono::system_clock::time_point _lastUpdateTime;
+    std::string _lastUpdateJsonString;
+
     std::chrono::milliseconds _skyBrowserUpdateTime = std::chrono::milliseconds(100);
 };