Docs: update the versions and links

CHANGELOG.md

@@ -3,7 +3,7 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning v2.0.0](https://semver.org/spec/v2.0.0.html).
 
-## [2.1.0] - 2023-07-14
+## [Unreleased] (2.1.0)
 ### Changed
 - AvaloniaMath is now based on (and thus compatible with) Avalonia 11.
 
@@ -320,4 +320,5 @@ This was the initially published version. It consisted entirely of the original
 [0.13.1]: https://github.com/ForNeVeR/xaml-math/compare/v0.13.0...v0.13.1
 [1.0.0]: https://github.com/ForNeVeR/xaml-math/compare/v0.13.1...v1.0.0
 [1.1.0]: https://github.com/ForNeVeR/xaml-math/compare/v1.0.0...v1.1.0
-[Unreleased]: https://github.com/ForNeVeR/xaml-math/compare/v1.1.0...HEAD
+[2.0.0]: https://github.com/ForNeVeR/xaml-math/compare/v1.1.0...v2.0.0
+[Unreleased]: https://github.com/ForNeVeR/xaml-math/compare/v2.0.0...HEAD