Support for using ToolbarAndroid in renderNavigationBar

[ide]

We're unlikely to build this because we optimize for iteration speed and customizability, so we greatly prefer code in JavaScript. renderNavigationBar lets you return whatever you want as long as it conforms to the NavigationBar interface, so you could implement your own custom navbar that uses an Android component.

[cancan101]

Looking over the code, routeMapper seems to have some hard assumptions, for example that the renderNavigationBar return value will render the title as a component rather than taking it as a text prop.