Dismiss the Keyboard when changing the page natively (Android)

This is already done in JS https://github.com/react-native-community/react-native-viewpager/blob/9a7b1a0a0528786832bd203e96e1826d2849b8fb/js/ViewPager.js#L106-L110

But we did it natively on iOS. Should be also easy to do it natively on Android: https://stackoverflow.com/a/11818992/2277631

Start with the linked JS/ViewPager.js lines 106-110 to understand the existing behavior, then locate the Android native pager implementation in this repository. Compare it with the native iOS handling mentioned in the issue and verify that changing pages dismisses the keyboard on Android. Done means the Android behavior matches the existing JS and iOS behavior.

Written by the indexing model from the issue text.