Add Drawer Navigation Snack expo example

[vikrantnegi]

While going through the documentation I found that drawer navigation is lacking snack expo example, unlike other navigation.
I know that it is obvious at that point on how to use the navigation but I think it would be of great help if there was a working example that we can edit on the fly.

Thanks.

[pinchez254]

noted the same..

[vickywane]

Here is a simple example demonstrating the drawer navigator.
https://snack.expo.io/Bk2HvmE-N