Use HTTPS for the "Keep a Changelog" link (#738)

Author: atouchet

CHANGELOG.md

@@ -1,7 +1,7 @@
 # Changelog
 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/)
+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).
 
 ## [0.3.4] - 2025-10-14