doc: add release notes (#206)

Signed-off-by: tygao <[email protected]>

release-notes/dashboards-assistant.release-notes-2.15.0.0.md

@@ -0,0 +1,12 @@
+## Version 2.15.0.0 Release Notes
+
+Compatible with OpenSearch and OpenSearch Dashboards Version 2.15.0
+
+### Experimental Features
+
+- Add data source service. ([#191](https://github.com/opensearch-project/dashboards-assistant/pull/191))
+- Update router and controller to support MDS. ([#190](https://github.com/opensearch-project/dashboards-assistant/pull/190))
+- Hide notebook feature when MDS enabled and remove security dashboard plugin dependency. ([#201](https://github.com/opensearch-project/dashboards-assistant/pull/201))
+- Refactor default data source retriever. ([#197](https://github.com/opensearch-project/dashboards-assistant/pull/197))
+- Reset chat and reload history after data source change. ([#194](https://github.com/opensearch-project/dashboards-assistant/pull/194))
+- Add patch style for fixed position components.([#203](https://github.com/opensearch-project/dashboards-assistant/pull/203))