Add changelog entry

ee/changelogs/unreleased-ee/epic-add-labels.yml

+---
+title: Allow to add or remove labels from epics and filter epics by labels
+merge_request: 4773
+author:
+type: added

ee/changelogs/unreleased/epic-add-labels.yml

----
-title: Allow adding or removing labels from epics and filter epics by labels
-merge_request:
-author:
-type: added