Apply native view switching animations

[AlanSl]

StackNavigator has built-in view transition animation, DrawerNavigator doesn't, so we lost the nice built-in iOS animations on switching to DrawerNavigator.

Adding such animations to DrawerNavigator would be a good accelerator-friendly example of how to apply custom transition animations that devs can build on.

React Navigation's default iOS stack animations are nice and should be emulated. The Android default animations are less impressive, so it might be worth doing some research to look for something with a native feel that is a bit better.

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I do not recommend using nested navigators for this. Many people use DrawerNavigator inside StackNavigator or StackNavigator inside DrawerNavigator as a quick-fix for things like this, but it has nasty side effects:

• Location params get lost between the outer and inner navigators
• Back button behaviour can become weird and iOS back button may be inappropriately missing or present
• React Navigation is quite locked down in some ways around how it renders output - basic things like stopping the Stack header from clashing with the drawer or changing which renders on top of the other can be surprisingly tricky or require hacks
• Cross-linking can be buggy or have unexpected behaviour

With just one non-nested navigator, it's easy to go anywhere from anywhere, and it's much easier to create simple similar developer experience for linking views in native and web.

[AlanSl]

I'm working on this alongside https://github.com/nearform/polaris/issues/42 as that requires some work on the native Navigator to stop it crashing Jest