New NavigationDrawer using kivy.garden.navigationdrawer

Here is the MD spec page for comparisons: https://material.io/guidelines/patterns/navigation-drawer.html#

Demo in KitchenSink, other NavDrawer things on the "Navigation Drawer Widgets" page.

Using garden.navigationdrawer, which allows for sliding in and out with a finger (like on android)

Also includes docs 😄