Add metrics to changelog

Author: frigus02

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+- Add support for metrics.
 - Take span resource into account for tags. Before a `service.name` in the resource would not populate the Cloud role name tag. Now it does.
 
 ## [0.17.0] - 2021-08-08