Adding placeholder for September 2020 release

Author: KoenZomers

CHANGELOG.md

@@ -5,6 +5,17 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
+## [3.25.2009.0] (not yet released)
+
+### Added
+
+
+### Changed
+
+
+### Contributors
+
+
 ## [3.24.2008.1]
 
 ### Added