Update release notes with latest merged feature

Author: bgandon

ci/release_notes.md

@@ -1,5 +1,6 @@
 ### Improvements
 
-- Improved code for easier maintenance
+- Have the resource fail when a message has faild to be posted on some channel (originally submitted in #97, thanks @Jazzepi)
+- Built resource image on top of latest Alpine v3.20.3
+- Improved code readability, for easier maintenance
 - Improved Concourse workflow, with continuous tests on the `develop` branch
-- Built resource image on top of Alpine 3.20.3