Update CHANGELOG to summarize data_loader changes

Author: Zaczero

CHANGELOG.md

@@ -8,6 +8,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Changed
+
+- Optimize data_loader.py script [#395](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/395)
+
+### Removed
+
+- Removed `requests` dev dependency [#395](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/395)
+
 ## [v5.0.0a1] - 2025-05-30
 
 ### Changed