Add changelog entry

Author: abcsds

CHANGELOG.md

@@ -1,3 +1,7 @@
+## [UNRELEASED] - 2025-01-08
+### ✨ Added
+- Add tests for string markers from issue xdf-modules/libxdf#19 (([#13](https://github.com/cbrnr/XDF.jl/pull/13) by [Alberto Barradas](https://github.com/abcsds)))
+ 
 ## [0.2.0] - 2022-02-23
 - Add support for string markers and string streams ([#2](https://github.com/cbrnr/XDF.jl/pull/2) by [Alberto Barradas](https://github.com/abcsds) and [Clemens Brunner](https://github.com/cbrnr))
 - Make header and footer XML available in "xml" key ([#4](https://github.com/cbrnr/XDF.jl/pull/4) by [Alberto Barradas](https://github.com/abcsds))