Add release notes for 1.3.16 (#13280) (#13286)

(cherry picked from commit c4843c9)

Signed-off-by: mgodwan <mgodwan@amazon.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: opensearch-trigger-bot[bot]

release-notes/opensearch.release-notes-1.3.16.md

@@ -0,0 +1,4 @@
+## 2024-04-18 Version 1.3.16 Release Notes
+
+### Upgrades
+- Bump `netty` from 4.1.107.Final to 4.1.109.Final ([#12924](https://github.com/opensearch-project/OpenSearch/pull/12924), [#13233](https://github.com/opensearch-project/OpenSearch/pull/13233))