text: importScripts('https://storage.googleapis.com/workbox-cdn/releases/4.3.1/workbox-sw.js');
  
  workbox.routing.registerRoute(
    /\.(?:js|css)$/,
    new workbox.strategies.StaleWhileRevalidate({
      cacheName: 'static-resources'
    })
  );
  
  workbox.routing.setDefaultHandler(
    new workbox.strategies.StaleWhileRevalidate()
  );
  