Added a related samples section for push notifications

service-worker/README.md

@@ -42,3 +42,7 @@ take control of the page that just registered it.
 
 - [Using `window.caches`](https://googlechrome.github.io/samples/service-worker/window-caches/index.html) -
 a sample showing how `window.caches` provides access to the Cache Storage API.
+
+# Related samples
+
+- Instructions for [registering for Push Messages and showing Notifications](https://github.com/GoogleChrome/samples/tree/gh-pages/push-messaging-and-notifications).