Forward-port v1.3.6 changelog

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

CHANGELOG.md

@@ -1,6 +1,13 @@
 # Changelog
 All notable changes to this project will be documented in this file.
 
+## 1.3.6 - 2020-06-30
+### Fixed
+- User data cleanup after account deletion
+- Navigating back on mobile
+- Formatting toggle in message composer
+- Missing `References` header for replies
+
 ## 1.4.0 - 2020-05-16
 ### Added
 - Priority Inbox: the combined inbox is now classified into important messages, favorites and others to keep you organized