Update CHANGELOG.md

Author: fverdugo

CHANGELOG.md

@@ -5,7 +5,13 @@ 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).
 
-## [0.4.1] - Unreleased
+## [Main branch]
+
+### Added
+
+- Enhancements in the logic behind the (undocumented) optional arguments in `psparse`, `pvector`, and `psystem`.
+
+## [0.4.1] - 2024-02-05
 
 ### Added