Add QtQuick app sample code

app/main.cpp

@@ -1,6 +1,10 @@
-#include <print>
+#include <QtGui>
+#include <QtQml>
 
-int main() {
-    std::println("Test\n");
-    return 0;
-}
+int main(int argc, char **argv) {
+  QGuiApplication app(argc, argv);
+  QUrl source(QStringLiteral("qrc:/qt/qml/app/main.qml"));
+  QQmlApplicationEngine engine;
+  engine.load(source);
+  return app.exec();
+}