Add support for onFocus prop

[chiaramooney]

Documentation

https://reactnative.dev/docs/touchablewithoutfeedback#onblur

Behavior

Handler invoked when component loses focus. This prop is only supported for some of the core component set. Take a look at the sub issues below to see which components should have their onBlur prop implemented.

We could use UIA data to determine when a component has gained focus. Possible helpful APIs:

Implementation Plan

We should:

1. Store the callback function for a component that has its onBlur prop set.
2. Create an event handler to monitor when the component incurs a focus event. When the focus event occurs, call the callback function.

To Be Clarified