flet-dev
Persist ```PopupMenu``` when clicking on checkbox items.
Currently, even when a checkbox item is selected from PopupMenu, it closes after the selection is made. This is not the expected behaviour for menus (for example, if you're toggling between dark/light mode, you would want to see the changes before exiting the menu. You might also want to make changes to other checkbox items before exiting the menu). When a checkbox is selected, there should be an option to allow the menu to persist.
A possible solution is to introduce a property for checkbox items with persist = True to keep the menu open in case that checkbox item is selected.
I haven't found how this is done in Flutter. Also, I don't think this is a behaviour accepted by M3.
