title: Authentication in a React Native WebView
body: <p>I have a working react-native application, which I would like to extend in a flexible way by adding a tab which displays a <code>WebView</code>. Here a user will be able to see their profile information, so I need to be able to authenticate each user.  </p>
  
  <p>I didn't think this would be difficult to implement since a user is already authenticated within the app, but apparently it is not possible to add custom headers to a WebView in react-native. And the same goes for the community component react-native-webview. So I cannot set an authorisation token on a request.</p>
  
  <p>This complicates the process of authentication, so I am looking for an alternative approach to do authentication within a WebView. To my surprise there isn't much information available on the web on how to do this. So what is a good approach to tackle auth in a react native <code>WebView</code>?</p>