Add example for using logging categories

QTProject/main.cpp

@@ -5,7 +5,11 @@
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
-    QLoggingCategory::setFilterRules("*.debug=false");
+    QLoggingCategory::setFilterRules("*.debug=false\n");
+
+    // If you want to enable debug output for some categories use something like this:
+    //QLoggingCategory::setFilterRules("*.debug=false\n"
+    //                                 "mesh.debug=true\n");
 
     MainWindow w;
     w.show();