Adding release notes for 2.8 (#918) (#919)

Signed-off-by: Martin Gaievski <gaievski@amazon.com>
(cherry picked from commit 556bb1a)

Co-authored-by: Martin Gaievski <gaievski@amazon.com>

Author: opensearch-trigger-bot[bot]

CHANGELOG.md

@@ -12,14 +12,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Maintenance
 ### Refactoring
 
-## [Unreleased 2.x](https://github.com/opensearch-project/k-NN/compare/2.7...2.x)
+## [Unreleased 2.x](https://github.com/opensearch-project/k-NN/compare/2.8...2.x)
 ### Features
 ### Enhancements
-* Bulk allocate objects for nmslib index creation to avoid malloc fragmentation ([#773](https://github.com/opensearch-project/k-NN/pull/773))
 ### Bug Fixes
 ### Infrastructure
-* Bump requests version from 2.26.0 to 2.31.0 ([#913](https://github.com/opensearch-project/k-NN/pull/913))
-* Disable index refresh for system indices ([#773](https://github.com/opensearch-project/k-NN/pull/915))
 ### Documentation
 ### Maintenance
 ### Refactoring

release-notes/opensearch-knn.release-notes-2.8.0.0.md

@@ -0,0 +1,12 @@
+## Version 2.8.0.0 Release Notes
+
+Compatible with OpenSearch 2.8.0
+
+### Enhancements
+
+* Bulk allocate objects for nmslib index creation to avoid malloc fragmentation ([#773](https://github.com/opensearch-project/k-NN/pull/773))
+
+### Infrastructure
+
+* Bump requests version from 2.26.0 to 2.31.0 ([#913](https://github.com/opensearch-project/k-NN/pull/913))
+* Disable index refresh for system indices ([#773](https://github.com/opensearch-project/k-NN/pull/915))