update CHANGELOG for 0.8.1

Author: orbeckst

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 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).
 
-## [0.8.1] - YYYY-MM-DD
+## [0.8.1] - 2021-10-01
 
 ### Added
 - docs for how to contribute a new dataset (#46)