Add changelog entry

Author: Ndpnt

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All changes that impact users of this module are documented in this file, in the [Common Changelog](https://common-changelog.org) format with some additional specifications defined in the CONTRIBUTING file. This codebase adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased [minor]
+
+### Added
+
+- Add a horizontal rule to delimit source documents when concatenating them to improve readability
+
 ## 7.0.0 - 2025-07-21
 
 _Full changeset and discussions: [#1175](https://github.com/OpenTermsArchive/engine/pull/1175)._