docs: add release note for the new itest

docs/release-notes/release-notes-0.16.0.md

@@ -144,6 +144,15 @@ crash](https://github.com/lightningnetwork/lnd/pull/7019).
   easily](https://github.com/lightningnetwork/lnd/pull/5561), in preparation for
   adding a data migration functionality to `lndinit`.
 
+### Integration test
+
+The `lntest` has been
+[refactored](https://github.com/lightningnetwork/lnd/pull/6759) to provide a
+better testing suite for writing integration tests. A new defined structure is
+implemented, please refer to
+[README](https://github.com/lightningnetwork/lnd/tree/master/lntemp) for more
+details.
+
 # Contributors (Alphabetical Order)
 
 * Carla Kirk-Cohen
@@ -161,3 +170,4 @@ crash](https://github.com/lightningnetwork/lnd/pull/7019).
 * Oliver Gugger
 * Priyansh Rastogi
 * Roei Erez
+* Yong Yu