Update CHANGELOG

Author: xrmx

CHANGELOG.md

@@ -16,6 +16,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `opentelemetry-instrumentation`: Avoid calls to `context.detach` with `None` token.
   ([#3673](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3673))
 
+### Added
+
+- `opentelemetry-instrumentation`: teach opentelemetry-instrument about gevent monkeypatching
+  ([#3699](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3699))
+
 ## Version 1.36.0/0.57b0 (2025-07-29)
 
 ### Fixed