core/window: make readonly bindable getters const

Author: bbedward

src/window/proxywindow.hpp

@@ -224,8 +224,8 @@ class ProxyWindowAttached: public QsWindowAttached {
 
 	[[nodiscard]] bool maximized() const override { return this->bMaximized; }
 	[[nodiscard]] bool fullscreen() const override { return this->bFullscreen; }
-	[[nodiscard]] QBindable<bool> bindableMaximized() override { return &this->bMaximized; }
-	[[nodiscard]] QBindable<bool> bindableFullscreen() override { return &this->bFullscreen; }
+	[[nodiscard]] QBindable<bool> bindableMaximized() const override { return &this->bMaximized; }
+	[[nodiscard]] QBindable<bool> bindableFullscreen() const override { return &this->bFullscreen; }
 
 protected:
 	void updateWindow() override;

src/window/windowinterface.hpp

@@ -281,8 +281,8 @@ class QsWindowAttached: public QObject {
 
 	[[nodiscard]] virtual bool maximized() const = 0;
 	[[nodiscard]] virtual bool fullscreen() const = 0;
-	[[nodiscard]] virtual QBindable<bool> bindableMaximized() = 0;
-	[[nodiscard]] virtual QBindable<bool> bindableFullscreen() = 0;
+	[[nodiscard]] virtual QBindable<bool> bindableMaximized() const = 0;
+	[[nodiscard]] virtual QBindable<bool> bindableFullscreen() const = 0;
 
 	Q_INVOKABLE [[nodiscard]] QPointF itemPosition(QQuickItem* item) const;
 	Q_INVOKABLE [[nodiscard]] QRectF itemRect(QQuickItem* item) const;