[FEAT] - Add method to get the input focus listener

[rpbarreira]

Is your feature request related to a problem? Please describe.

I need to programmatically add or remove the focus event listener from the bounded input, so I need to get it from the kioskboard to pass it as the listener to the "addEventListener" or "removeEventListener" methods

Describe the solution you'd like

A method on the KioskBoard namespace that returns the input focus listener