docs: record metadata update in changelog

Author: nagkumar91

instrumentation-genai/opentelemetry-instrumentation-openai-agents-v2/CHANGELOG.md

@@ -6,6 +6,8 @@ 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).
 
 ## Unreleased
+- Document official package metadata and README for the OpenAI Agents instrumentation.
+  ([#3859](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3859))
 
 ## Version 0.1.0 (2025-10-15)