Update CHANGELOG.md

Author: mvdnbrk

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to `dhlparcel-php-api` will be documented in this file.
 
 ## [Unreleased]
 
+## [v1.4.0] - 2020-12-18
+
+### Added
+- Support for PHP 8. [`#60`](https://github.com/mvdnbrk/dhlparcel-php-api/pull/60)
+
 ## [v1.3.1] - 2020-12-17
 
 ### Fixed
@@ -155,7 +160,8 @@ All notable changes to `dhlparcel-php-api` will be documented in this file.
 
 ### Initial release
 
-[Unreleased]: https://github.com/mvdnbrk/dhlparcel-php-api/compare/v1.3.1...HEAD
+[Unreleased]: https://github.com/mvdnbrk/dhlparcel-php-api/compare/v1.4.0...HEAD
+[v1.4.0]: https://github.com/mvdnbrk/dhlparcel-php-api/compare/v1.3.1...v1.4.0
 [v1.3.1]: https://github.com/mvdnbrk/dhlparcel-php-api/compare/v1.3.0...v1.3.1
 [v1.3.0]: https://github.com/mvdnbrk/dhlparcel-php-api/compare/v1.2.1...v1.3.0
 [v1.2.1]: https://github.com/mvdnbrk/dhlparcel-php-api/compare/v1.2.0...v1.2.1