Keep the burger icon visible after opening the drawer

If you open the Drawer menu, the only way to close it is by clicking outside it.
I think it would be helpful to always see the Drawer menu icon.
When you click on it you should be able to display and also hide the menu.

This would be very helpful for mobile devices, where you have a limited view (smaller resolution than a monitor).
If you have a very small screen resolution you can even get blocked in Drawer menu.