Update CHANGELOG.md

Signed-off-by: Arnaldo Cesco <arnaldo.cesco@secomind.com>

CHANGELOG.md

@@ -4,6 +4,17 @@ 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/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [23.5.1] - Unreleased
+### Added
+- Backported addition of `realm-management interfaces {sync, save}` to batch
+  install or download triggers.
+- Backported addition of `appengine device {publish-datastream,
+  set-property, unset-property}` to send data to Astarte.
+
+### Changed
+- Backported deprecation of `appengine device send-data`, use
+  `{publish-datastream, set-property, unset-property}` instead.
+
 ## [23.5.0] - 2023-10-04
 ### Added
 - Add fish shell completions generator command