Added 2.18.0 release notes. (#980) (#981)

(cherry picked from commit ddfcd3d)

Signed-off-by: AWSHurneyt <hurneyt@amazon.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: opensearch-trigger-bot[bot]

release-notes/opensearch-notifications.release-notes-2.18.0.0.md

@@ -0,0 +1,10 @@
+## Version 2.18.0.0 2024-10-28
+
+Compatible with OpenSearch 2.18.0
+
+### Maintenance
+* Increment version to 2.18.0-SNAPSHOT ([#957](https://github.com/opensearch-project/notifications/pull/957))
+* updated workflows to fix CIs ([#965](https://github.com/opensearch-project/notifications/pull/965))
+
+### Documentation
+* Add 2.18.0 release notes ([#980](https://github.com/opensearch-project/notifications/pull/980))