Update changelog.

Author: Kami

CHANGELOG.md

@@ -8,6 +8,8 @@ For actual scalyr agent changelog, please see https://github.com/scalyr/scalyr-a
   value for the agent ``secretKeyRef`` ``name`` field value. When not set, ``secretKeyRef``
   ``name`` field value defaults to ``{{ include "scalyr-helm.fullname" . }}-scalyr-api-key``.
 
+  This allows users to re-use the existing Kubernetes secret where DataSet API key is stored.
+
 ## 0.2.20
 
 - Update agent to the latest stable version (v2.1.36).