showDragHandle

Whether to overlay a drag handle in the bottom sheet.

The handle will be overlaid over property@BottomSheet:sheet.

When the handle is shown, class@HeaderBar will hide its default title, and class@ToolbarView will reserve space if there are no top bars.

Showing drag handle also allows to swipe the bottom sheet down (and to swipe the bottom bar up) with a pointer, instead of just touchscreen.