Add link

docs/GCP/Identity-Aware Proxy/port-forwarding.md

@@ -16,4 +16,6 @@ Before each session you may launch, make sure to be **authenticated with your gc
 
 If for instance, I am testing the great vectr purple team's app on a cloud-based instance. The frontend will be by default running on localhost:8501. As a result, I'll able to redirect such traffic to my local machine thanks to this command.
 
-<pre>gcloud compute start-iap-tunnel vectr-test-instance 8501     --local-host-port=localhost:8501</pre>
+<pre>gcloud compute start-iap-tunnel vectr-test-instance 8501     --local-host-port=localhost:8501</pre>
+
+[Official documentation](https://cloud.google.com/solutions/connecting-securely#:~:text=or%20SOCKS%20proxy.-,Port%20forwarding%20over%20SSH,host%20over%20an%20SSH%20connection.&text=LOCAL_PORT%20%3Alocalhost%3A%20REMOTE_PORT-,Replace%20the%20following%3A,your%20Google%20Cloud%20project%20ID.)