update the link to the gitter chat

Author: stevehu

README.md

@@ -1,6 +1,6 @@
 [Stack Overflow](https://stackoverflow.com/questions/tagged/light-4j) |
 [Google Group](https://groups.google.com/forum/#!forum/light-4j) |
-[Gitter Chat](https://gitter.im/networknt/light-rest-4j) |
+[Gitter Chat](https://gitter.im/networknt/json-schema-validator) |
 [Subreddit](https://www.reddit.com/r/lightapi/) |
 [Youtube](https://www.youtube.com/channel/UCHCRMWJVXw8iB7zKxF55Byw) |
 [Documentation](https://doc.networknt.com/library/json-schema-validator/) |