Add service worker api link

Author: satyam-seth

index.html

@@ -98,5 +98,6 @@
     <a href="./Audio Visualizer/demo.html">Audio Visualizer</a>
     <a href="./OTP Input Field/index.html">OTP Input Field</a>
     <a href="./Broadcast Channel API/demo.html">Broadcast Channel API</a>
+    <a href="./Service Worker API/demo.html">Service Worker API</a>
   </body>
 </html>