qtquick: Add missing isMDI Q_PROPERTY

src/qtquick/views/Frame_qtquick.cpp

@@ -228,3 +228,8 @@ QRect Frame_qtquick::dragRect() const
     qFatal("Not implemented");
     return {};
 }
+
+bool Frame_qtquick::isMDI() const
+{
+    return m_controller->isMDI();
+}

src/qtquick/views/Frame_qtquick.h

@@ -34,6 +34,7 @@ class DOCKS_EXPORT Frame_qtquick : public View_qtquick, public Frame
 {
     Q_OBJECT
     Q_PROPERTY(QObject *tabWidget READ tabWidgetObj CONSTANT)
+    Q_PROPERTY(bool isMDI READ isMDI CONSTANT)
 public:
     explicit Frame_qtquick(Controllers::Frame *controller, QQuickItem *parent = nullptr);
     ~Frame_qtquick() override;
@@ -53,6 +54,10 @@ public:
 
     QRect dragRect() const override;
 
+
+    // QML interface:
+    bool isMDI() const;
+
 protected:
     void removeWidget_impl(Controllers::DockWidget *) override;
     int indexOfDockWidget_impl(const Controllers::DockWidget *) override;