make SafeAreaView can be used in iOS version pre-11 (eg: iOS 9 and iOS 10)
$ yarn add with-safe-area
// @flow
import * as React from 'react';
import WithSafeArea from 'with-safe-area';
import AppRouter from './AppNavigator';
export default class App extends React.Component {
render() {
return (
<WithSafeArea>
<AppRouter />
</WithSafeArea>
);
}
}