Finish customize system button pos for QtWidgets

SineStriker

2023-12-27 2f2ee6571e9ce784db0488ade60816f09bd7448c

 examples/mainwindow/mainwindow.h

@@ -28,6 +28,7 @@

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

    Theme currentTheme{};