docs: release 0.7.0

Author: tpetry

CHANGELOG.md

@@ -5,6 +5,10 @@ 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).
 
+## [0.7.0] - 2023-09-01
+### Added
+* `Upper` and `Lower` string transformations
+
 ## [0.6.0] - 2023-08-31
 ### Added
 * `Count` aggregate has an optional distinct parameter