Popups
  To implement the popup, use the following markup. It corresponds accessibility requirements. To set Popup styles use the .lib-popup() mixin.
  The .lib-window-overlay() mixin controls the styles of overlay background.
Simple popup
Popup with actions toolbar
.window.popup.popup-example {
    .lib-popup();
}
.window.popup.popup-example-1 {
    .lib-popup();
}
.window.overlay {
    .lib-window-overlay();
}