UI: Set desktopFileName for QApplication

This needs to match the base name of the .desktop file name.

This is needed for propagating the correct App ID on Wayland,
which is needed e.g. for proper window icons on Plasma.

UI/obs-app.cpp

@@ -1164,6 +1164,8 @@ OBSApp::OBSApp(int &argc, char **argv, profiler_name_store_t *store)
 #else
 	setWindowIcon(QIcon::fromTheme("obs", QIcon(":/res/images/obs.png")));
 #endif
+
+	setDesktopFileName("com.obsproject.Studio");
 }
 
 OBSApp::~OBSApp()