title: UpUp to force the offline.html even when online
body: <p>So I am trying to use the UpUp library to build a offline first webpage.</p>
  
  <p>The library shows the offline page when I am offline. How do i force UpUp to show the offline page irrespective of being online or offline.</p>
  
  <p>What I am trying to do is build something like, the app shell will always be loaded from the service worker cache and the network calls be made from there. That would make my app load much faster as the initial page load won't be from the web.</p>