Improve accessibility support

[pierpo]

Is your feature request related to a problem? Please describe.
For now, we just provide a hack for Android, and no solution for iOS/web.

Describe the solution you'd like
The hard part with accessibility is that we override the whole native navigation system. It's hard to plug our system into this.
We try to listen for accessibility focus events and sync our lib with it, but it's not completely satisfying.

Better accessibility support is required, and it still needs some thinking.

This React Native PR is necessary for this purpose.

facebook/react-native#41336