adds link to loopback address

Author: ishtms

chapters/ch06.0-http-deep-dive.md

@@ -82,7 +82,7 @@ server.listen(3000, "127.0.0.1");
 
 You can also use the IP address `'127.0.0.1'` instead of `'localhost'` to achieve the same result.
 
-Both **`localhost`** and **`127.0.0.1`** refer to the local loopback address, which means that the server will only be accessible from the same machine it's running on. This is commonly used by developers for testing and debugging purposes.
+Both **`localhost`** and **`127.0.0.1`** refer to the local [loopback address](https://en.wikipedia.org/wiki/Localhost#Loopback), which means that the server will only be accessible from the same machine it's running on. This is commonly used by developers for testing and debugging purposes.
 
 In fact, it's a best practice to develop and test applications locally before deploying them to a production environment, as it allows for easier troubleshooting and debugging of any issues that may arise.