old_contents: // JavaScript Document
  
  // Scripts written by YOURNAME @ YOURCOMPANY
  
  toolbox.precache(["/", "../styles/modern.css"]);
  toolbox.router.get("../media/*", toolbox.cacheFirst);
  toolbox.router.get("/wp-content/uploads/*", toolbox.cacheFirst);
  toolbox.router.get("/*", toolbox.networkFirst, {NetworkTimeoutSeconds: 5});
  
new_contents: // JavaScript Document
  
  // Scripts written by YOURNAME @ YOURCOMPANY
  
  toolbox.precache(["?utm_source=pwa", "../styles/modern.css"]);
  toolbox.router.get("../media/*", toolbox.cacheFirst);
  toolbox.router.get("/wp-content/uploads/*", toolbox.cacheFirst);
  toolbox.router.get("/*", toolbox.networkFirst, {NetworkTimeoutSeconds: 5});
  
subject: Update root URL in service worker to have utm_source