add result to popToNative

[sjwall]

Hey, thank you for the great work on this library, it has been super useful

Summary

Allows data to be passed back to native within the lifecycle.
A use case example is if the user was asked a question in react native, returning the result to action that in native.

Adds a result param to popToNative.
On android result is accessible in the activity result.
On iOS result is accessible in the popToNative notification broadcast.

An alternative approach would be to build this out in a separate library or have a shared storage solution

Test plan

In the example app the popToNative call has a result value added
Running the example on iOS in the logs it will print the result

Running on Android it will show a popup

Let me know what you think and if there's anything that can be done to improve it :)