feat: adds open in gitpod button

Author: anugrahsinghal

README.md

@@ -13,3 +13,6 @@ For any queries, or support requests, please email us at [email protected], or
 
 # Authors
 Created with :heart: by the folks at SuperTokens.io.
+
+# Contribute
+[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/from-referrer/)