Add changelog entry

Signed-off-by: Cedric Willekens <c.s.willekens@student.tudelft.nl>

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 ### Fixed
+- Correctly sort claimed time slots in admin view [@cedricwilleken](https://gitlab.ewi.tudelft.nl/cedricwilleken)
 
 ## [1.2.0] - (2020-05-20)
 ### Added