Update CHANGELOG.md

Author: gkjohnson

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [0.3.10] - 2025-06-22
+### Added
+- Support for "tau" in expressions.
+
 ## [0.3.9] - 2022-11-19
 ### Added
 - Exposed the expression parser so functions can be added and extended.