Added release notes for 2.12 (#1800) (#1802)

(cherry picked from commit 2ef7adc)

Signed-off-by: Shenoy Pratik <sgguruda@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>

release-notes/opensearch-observability.release-notes-2.12.0.0.md

@@ -0,0 +1,22 @@
+## Version 2.12.0.0 Release Notes
+
+Compatible with OpenSearch 2.12.0
+
+### Features
+
+- Add metric type ([#1775](https://github.com/opensearch-project/observability/pull/1775))
+
+### Maintainance
+
+- Upgrade gradle to 8.5 ([#1777](https://github.com/opensearch-project/observability/pull/1777))
+- Remove integration content ([#1738](https://github.com/opensearch-project/observability/pull/1738))
+- Manually Force Secure logback Dependencies ([#1795](https://github.com/opensearch-project/observability/pull/1795))
+
+### Bug Fixes
+
+- Upgrade JSON to 20231013 to fix CVE-2023-5072 ([#1750](https://github.com/opensearch-project/observability/pull/1750))
+- Bumping ktlint and resolving conflicts ([#1792](https://github.com/opensearch-project/observability/pull/1792))
+
+### Infrastructure
+
+- Onboard jenkins prod docker images on github actions ([#1763](https://github.com/opensearch-project/observability/pull/1763))