docs: update CHANGELOG

Author: BriannaDelgado

CHANGELOG.md

@@ -5,6 +5,13 @@ 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]
+### Added
+- Added support for translation memories in text translation via
+  `translationMemory` and `translationMemoryThreshold` options in
+  `translateText()`.
+- Added `listTranslationMemories()` method to the `DeepLClient` class for
+  listing available translation memories.
+
 ### Fixed
 - Fix write tests that broke from language expansion