Add 1.3.1 release notes (#1713)

Signed-off-by: cliu123 <lc12251109@gmail.com>

Author: cliu123

release-notes/opensearch-security.release-notes-1.3.1.0.md

@@ -0,0 +1,12 @@
+## 2022-03-30 Version 1.3.1.0
+
+Compatible with OpenSearch 1.3.1
+
+### Bug fixes
+
+* Fix min_doc_count handling when using Document Level Security ([#1712](https://github.com/opensearch-project/security/pull/1712))
+
+### Maintenance
+
+* Bump plugin version to 1.3.1.0 and OpenSearch dependency version to 1.3.1 ([#1697](https://github.com/opensearch-project/security/pull/1697))
+* Add 1.3.1 release notes ([#1713](https://github.com/opensearch-project/security/pull/1713))