add macos titlebar

Zhao Yuhang

2023-12-14 2452f5958272d50981ab89ff843d2fa715d33957

 src/widgets/widgetwindowagent_p.h

@@ -19,6 +19,8 @@

#ifdef Q_OS_WINDOWS
        void setupWindows10BorderWorkaround();
#elif defined(Q_OS_MACOS)
        void setupMacOSTitleBar(QWidget *titleBar);
#endif
    };