make demo a GUI application in CMake

Yuhang Zhao

2025-02-10 9e96ea43436d5ed200c57d6b229cddf9bdf9e55a

 examples/mainwindow/light-style.qss

@@ -1,11 +1,13 @@
/* Window bar */

QWK--WindowBar[bar-active=true] {
    background-color: #195ABE;
    /*background-color: #195ABE;*/
    background-color: transparent;
}

QWK--WindowBar[bar-active=false] {
    background-color: #195ABE;
    /*background-color: #195ABE;*/
    background-color: transparent;
}