add Unreleased section back to CHANGELOG.md post-release

Author: kemccusker

CHANGELOG.md

@@ -5,7 +5,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
-## [0.7.0] - 2025-08-14
+## Unreleased
+
+
+## [0.7.0] - 2025-08-15
 
 ### Added
 - [Documentation pages](climateimpactlab.github.io/dscim/) added using mkdocs ([PR #254](https://github.com/ClimateImpactLab/dscim/pull/254), [@JMGilbert](https://github.com/JMGilbert))