Add link to release

Author: aaron-lane

CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 Extending the adopted spec, each change should have a link to its corresponding pull request appended.
 
+## [Unreleased]
+
 ## [2.1.0] - 2019-03-11
 
 ### ADDED
@@ -89,7 +91,8 @@ Extending the adopted spec, each change should have a link to its corresponding
 ### ADDED
 - This is the initial release of the Project Factory Module.
 
-[Unreleased]: https://github.com/terraform-google-modules/terraform-google-project-factory/compare/v2.0.0...HEAD
+[Unreleased]: https://github.com/terraform-google-modules/terraform-google-project-factory/compare/v2.1.0...HEAD
+[2.1.0]: https://github.com/terraform-google-modules/terraform-google-project-factory/compare/v2.0.0...v2.1.0
 [2.0.0]: https://github.com/terraform-google-modules/terraform-google-project-factory/compare/v1.2.0...v2.0.0
 [1.2.0]: https://github.com/terraform-google-modules/terraform-google-project-factory/compare/v1.1.2...v1.2.0
 [1.1.2]: https://github.com/terraform-google-modules/terraform-google-project-factory/compare/v1.1.1...v1.1.2