docs: release 0.9.0

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).
 
+## [0.9.0] - 2023-11-30
+### Added
+* Case-when syntax
+
 ## [0.8.0] - 2023-11-10
 ### Added
 * `Abs` mathematical function