Update changelog

Author: david-sawatzke

CHANGELOG.md

@@ -5,6 +5,8 @@ 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).
 
 ## [Unreleased]
+
+## [0.3.1] - 2024-01-22
 ### Added
 - Async variant of the trait. This should be seen as an addition to the synchronous implementation