Add to changelog

Signed-off-by: Thomas Farr <tsfarr@amazon.com>

CHANGELOG.md

@@ -2,6 +2,9 @@
 Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased]
+### ⚠️ Breaking Changes ⚠️
+- Moved `OpenSearch.Client` request classes into their respective namespaces to match those in `OpenSearch.Net` ([#209](https://github.com/opensearch-project/opensearch-net/pull/209))
+
 ### Dependencies
 - Bumps `System.Reflection.Emit` from 4.3.0 to 4.7.0
 - Bumps `Argu` from 5.5.0 to 6.1.1
@@ -53,4 +56,4 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Bumps `Microsoft.NETFramework.ReferenceAssemblies` from 1.0.0-preview.2 to 1.0.3
 
 [Unreleased]: https://github.com/opensearch-project/opensearch-net/compare/1.3.0...HEAD
-[1.3.0]: https://github.com/opensearch-project/opensearch-net/compare/1.2.0...1.3.0
+[1.3.0]: https://github.com/opensearch-project/opensearch-net/compare/1.2.0...1.3.0