Add support for `ReactEvent.Keyboard.stopImmediatePropagation` binding

[sinap-fb]

[Christoph Knittel]

@sinap-fb Are you sure that this actually exists on React Synthetic Events?

It is neither in the React docs (https://reactjs.org/docs/events.html) nor in the TypeScript typedefs (https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/react/index.d.ts).

I think it only exist on the underlying nativeEvent, but that is currently only typed as

  @get external nativeEvent: Type.t => {..} = "nativeEvent" /* Should return Dom.event */

Also it is not Keyboard-specific as far as I can see.

[Christoph Knittel]

Closing. @sinap-fb feel free to ping me if this is still relevant for you.