Add CHANGELOG entry

CHANGELOG

@@ -75,6 +75,7 @@ v 8.7.0 (unreleased)
   - Fix emoji categories in the emoji picker
   - Add encrypted credentials for imported projects and migrate old ones
   - Author and participants are displayed first on users autocompletion
+  - Show number sign on external issue reference text (Florent Baldino)
 v 8.6.6
   - Expire the exists cache before deletion to ensure project dir actually exists (Stan Hu). !3413