update CHANGELOG for version 0.4.0

Author: joshuadavidthomas

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project attempts to adhere to [Semantic Versioning](https://semver.org/
 
 ## [Unreleased]
 
+## [0.4.0]
+
 ## [0.3.0]
 
 ### Added
@@ -60,8 +62,9 @@ and this project attempts to adhere to [Semantic Versioning](https://semver.org/
 
 - Josh Thomas <[email protected]> (maintainer)
 
-[unreleased]: https://github.com/joshuadavidthomas/django-github-app/compare/v0.3.0...HEAD
+[unreleased]: https://github.com/joshuadavidthomas/django-github-app/compare/v0.4.0...HEAD
 [0.1.0]: https://github.com/joshuadavidthomas/django-github-app/releases/tag/v0.1.0
 [0.2.0]: https://github.com/joshuadavidthomas/django-github-app/releases/tag/v0.2.0
 [0.2.1]: https://github.com/joshuadavidthomas/django-github-app/releases/tag/v0.2.1
 [0.3.0]: https://github.com/joshuadavidthomas/django-github-app/releases/tag/v0.3.0
+[0.4.0]: https://github.com/joshuadavidthomas/django-github-app/releases/tag/v0.4.0