docs: add docs for #135

docs/modules/workbox.md

@@ -160,3 +160,28 @@ workbox: {
   ],
 }
 ```
+
+### Hooking on service worker registration life cycle
+
+Create `plugins/sw.js`:
+
+```js
+if ('serviceWorker' in navigator) {
+  navigator.serviceWorker.getRegistrations().then((registrations) => {
+    for (const worker of registrations) {
+      console.log('Service worker:', worker)
+    }
+  });
+}
+```
+
+Add it to the `plugins` section of `nuxt.config.js`:
+
+```js
+{
+  plugins: [
+    src: '~/plugins/sw.js',
+    ssr: false
+  ]
+}
+```