add 1.3.1 release notes (opensearch-project#263)

Signed-off-by: Yaliang Wu <[email protected]>

Author: ylwu-amzn

Diff for: release-notes/opensearch-ml-common.release-notes-1.3.1.0.md

@@ -0,0 +1,15 @@
+## Version 1.3.1.0 Release Notes
+
+Compatible with OpenSearch 1.3.1
+
+### Enhancements
+
+* use protostuff to serialize/deserialize RCF model ([#251](https://github.com/opensearch-project/ml-commons/pull/251))
+
+### Infrastructure
+
+* use latest RCF jar ([#259](https://github.com/opensearch-project/ml-commons/pull/259))
+
+### Maintenance
+
+* bump to 1.3.1 ([#254](https://github.com/opensearch-project/ml-commons/pull/254))