Cleaner "Offer a page reload for users" recipe

Since Workbox v6 a new method, messageSkipWaiting(), has been added to the workbox-window module to simplify the process of telling the "waiting" service worker to activate. And all "external" events in workbox-window have been removed in place of "normal" events with an isExternal property set to true. Thanks to both of the above changes, the "Offer a page reload for users" recipe can be simplified.

Author: ghpranav

examples/lifecycle/pages/index.js

@@ -37,7 +37,7 @@ export default () => {
           })
 
           // Send a message to the waiting service worker, instructing it to activate.
-          wb.messageSW({ type: 'SKIP_WAITING' })
+          wb.messageSkipWaiting()
         } else {
           console.log(
             'User rejected to reload the web app, keep using old version. New version will be automatically load when user open the app next time.'
@@ -46,7 +46,6 @@ export default () => {
       }
 
       wb.addEventListener('waiting', promptNewVersionAvailable)
-      wb.addEventListener('externalwaiting', promptNewVersionAvailable)
 
       // ISSUE - this is not working as expected, why?
       // I could only make message event listenser work when I manually add this listenser into sw.js file