Update Readme with instructions for running the code

Author: agmo

README.md

@@ -3,3 +3,13 @@ Experimenting with the Notifications API and the Web Push API
 # Links
 
 [Deep Dive into Web Push Notifications by Harit Himanshu](https://app.pluralsight.com/library/courses/web-push-notifications-deep-dive/table-of-contents)
+
+# To run the code
+
+1. Run
+
+ ```
+ npm start
+ ```
+
+1. Browse to http://localhost:3000/`