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