Use AA_UseHighDpiPixmaps in the example

it's a best practice

examples/basic/main.cpp

@@ -90,6 +90,7 @@ public:
 int main(int argc, char **argv)
 {
     QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+    QApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
     QApplication app(argc, argv);
     app.setOrganizationName(QStringLiteral("KDAB"));
     app.setApplicationName(QStringLiteral("Test app"));