docs: update changelog for v0.3.8 release

Author: Nicholas Cecere

CHANGELOG.md

@@ -5,6 +5,15 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.3.8] - 2025-08-08
+
+### Added
+- Added `additional_litellm_params` field to model resource for custom parameters beyond standard ones
+- Support for passing custom parameters like `drop_params`, `timeout`, `max_retries`, `organization`, etc.
+- Automatic type conversion for string values to appropriate types (boolean, integer, float)
+- Full backward compatibility with existing model configurations
+- Comprehensive example demonstrating various use cases with different providers
+
 ## [0.3.7] - 2025-08-08
 
 ### Fixed