fix: changelog

CHANGELOG.md

@@ -12,6 +12,7 @@
 * [BUGFIX] Fixed `CortexIngesterHasNotShippedBlocks` alert false positive in case an ingester instance had ingested samples in the past, then no traffic was received for a long period and then it started receiving samples again. #308
 * [CHANGE] Dashboards: added overridable `job_labels` and `cluster_labels` to the configuration object as label lists to uniquely identify jobs and clusters in the metric names and group-by lists in dashboards. #319
 * [CHANGE] Dashboards: `alert_aggregation_labels` has been removed from the configuration and overriding this value has been deprecated. Instead the labels are now defined by the `cluster_labels` list, and should be overridden accordingly through that list. #319
+* [ENHANCEMENT] Added documentation text panels and descriptions to Reads and Writes dashboards. 
 
 ## 1.9.0 / 2021-05-18