add missing Win10 API

Zhao Yuhang

2025-03-09 a1c500e1dd254445e7bc153f4e0f049cabab35a0

 examples/mainwindow/mainwindow.h

@@ -30,8 +30,6 @@
protected:
    bool event(QEvent *event) override;

    void closeEvent(QCloseEvent *event) override;

private:
    void installWindowAgent();
    void loadStyleSheet(Theme theme);