update demo code

Zhao Yuhang

2024-09-15 f645ae48cda10b80ffe9d83ba9487671c7f535c0

 examples/mainwindow/light-style.qss

@@ -144,6 +144,10 @@
    background-color: #F3F3F3;
}

MainWindow[custom-style=true] {
    background-color: transparent;
}

QWidget#clock-widget {
    font-size: 75px;
    color: #333333;