Upgrade to React Navigation 5

[lesmo]

Addresses #7, so we'll now be using the latest stable version of React Navigation.

I'm not comfortable releasing this yet, as using the browser's history to move forward and back the second time raises this error:

The action 'RESET' with payload {"stale":false,"type":"stack","key":"stack-YDUoxSrlp7c_rSKXZ7GNw","index":1,"routeNames":["Home","Details"],"routes":[{"name":"Home","key":"Home-Y4E99beLSgaS3IhUFWdM7","params":{}},{"key":"Details-9CYFzWkM6ifCWd88-kRgE","name":"Details","params":{}}]} was not handled by any navigator.

This is a development-only warning and won't be shown in production.

I'm unsure what's the root cause, and I might open an issue on React Navigation's repo.

[lesmo]

Waiting on react-navigation/react-navigation#9408