add release notes for 3.0-alpha1 (#728)

Signed-off-by: will-hwang <sang7239@gmail.com>

CHANGELOG.md

@@ -4,16 +4,13 @@ All notable changes to this project are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). 
 See the [CONTRIBUTING guide](./CONTRIBUTING.md#Changelog) for instructions on how to add changelog entries.
 
-## [Unreleased 3.0](https://github.com/opensearch-project/geospatial/compare/2.x...HEAD)
+## [Unreleased 3.x](https://github.com/opensearch-project/geospatial/compare/main...HEAD)
 ### Features
 ### Enhancements
 ### Bug Fixes
 ### Infrastructure
 ### Documentation
 ### Maintenance
-- Set geospatial plugin 3.0.0 baseline JDK version to JDK-21 ([#695](https://github.com/opensearch-project/geospatial/pull/695))
-- Bump gradle 8.10.2 / JDK 23 / 3.0.0.0-alpha1 support on geospatial ([#723](https://github.com/opensearch-project/geospatial/pull/723)) 
-
 ### Refactoring
 
 ## [Unreleased 2.x](https://github.com/opensearch-project/geospatial/compare/2.19...2.x)

release-notes/opensearch-geospatial.release-notes-3.0.0.0-alpha1.md

@@ -0,0 +1,7 @@
+## Version 3.0.0.0-alpha1 Release Notes
+
+Compatible with OpenSearch 3.0.0.0-alpha1
+
+### Maintenance
+* Set geospatial plugin 3.0.0 baseline JDK version to JDK-21 ([#695](https://github.com/opensearch-project/geospatial/pull/695))
+* Bump gradle 8.10.2 / JDK 23 / 3.0.0.0-alpha1 support on geospatial ([#723](https://github.com/opensearch-project/geospatial/pull/723))