chore: add "Unreleased" to CHANGELOG (#86)

CHANGELOG.md

@@ -5,6 +5,8 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
 ## [0.1.15] - 2024-12-07
 
 ### Changed
@@ -111,6 +113,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add CIDR unmarshalling and validation
 - Add autonomous systems to configuration
 
+[Unreleased]: https://github.com/danroc/geoblock/compare/v0.1.15...HEAD
 [0.1.15]: https://github.com/danroc/geoblock/compare/v0.1.14...v0.1.15
 [0.1.14]: https://github.com/danroc/geoblock/compare/v0.1.13...v0.1.14
 [0.1.13]: https://github.com/danroc/geoblock/compare/v0.1.12...v0.1.13