Added missing version links

Author: brainandforce

CHANGELOG.md

@@ -5,7 +5,7 @@ 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](https://semver.org/spec/v2.0.0.html).
 
-## Unreleased
+## [Unreleased]
 
 ## Added
   - New methods: `NormalForms.is_row_zero_after`, `NormalForms.is_col_zero_after`, 
@@ -76,3 +76,11 @@ able to become zero off-diagonal.
 ## [0.1.0] - 2022-11-07
 
 Initial release - added to Julia package registry
+
+[Unreleased]: https://github.com/brainandforce/NormalForms.jl
+[0.1.5]: https://github.com/brainandforce/NormalForms.jl/releases/tag/v0.1.5
+[0.1.4]: https://github.com/brainandforce/NormalForms.jl/releases/tag/v0.1.4
+[0.1.3]: https://github.com/brainandforce/NormalForms.jl/releases/tag/v0.1.3
+[0.1.2]: https://github.com/brainandforce/NormalForms.jl/releases/tag/v0.1.2
+[0.1.1]: https://github.com/brainandforce/NormalForms.jl/releases/tag/v0.1.1
+[0.1.0]: https://github.com/brainandforce/NormalForms.jl/releases/tag/v0.1.0