Add release notes for 3.1.0 (#756) (#759)

Signed-off-by: Bo Zhang <bzhangam@amazon.com>

Author: bzhangam

CHANGELOG.md

@@ -11,14 +11,4 @@ See the [CONTRIBUTING guide](./CONTRIBUTING.md#Changelog) for instructions on ho
 ### Infrastructure
 ### Documentation
 ### Maintenance
-Fix a unit test and update github workflow to use actions/setup-java@v3.
-### Refactoring
-
-## [Unreleased 2.x](https://github.com/opensearch-project/geospatial/compare/2.19...2.x)
-### Features
-### Enhancements
-### Bug Fixes
-### Infrastructure
-### Documentation
-### Maintenance
 ### Refactoring

release-notes/opensearch-geospatial.release-notes-3.1.0.0.md

@@ -0,0 +1,6 @@
+## Version 3.1.0.0 Release Notes
+
+Compatible with OpenSearch 3.1.0
+
+### Maintenance
+Fix a unit test and update github workflow to use actions/setup-java@v3.