[skip ci] update changelog

Author: Ruairi Moran

CHANGELOG.md

@@ -6,6 +6,16 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+<!-- ---------------------
+      v1.2.1
+     --------------------- -->
+## v1.2.1 - 07-10-2024
+
+### Added
+
+- Patch initialisation of Q in QR decomposition.
+- Add test for tall skinny matrices.
+
 <!-- ---------------------
       v1.2.0
      --------------------- -->