From https://github.com/react-native-community/react-native-webview
As discussed in react-native-community/discussions-and-proposals#6
and react-native-community/discussions-and-proposals#3

Create injected JavaScript in a single place and then inject it both as
a WebView prop and with the `injectJavaScript`-method on `onLoadEnd`.
This is preparatory for adding more injected JavaScript.

Opens external links present onLoadEnd in external browser, but doesn't
yet handle the SPA-aspect of the site