Add message to PR when merging release branch

Author: thomaseizinger

.github/workflows/publish-new-release.yml

@@ -45,5 +45,8 @@ jobs:
           head: release/${{ env.RELEASE_VERSION }}
           base: dev
           title: Merge release ${{ env.RELEASE_VERSION }} into dev branch
+          body: |
+            This PR merges the release branch for ${{ env.RELEASE_VERSION }} back into dev.
+            This happens to ensure that the updates that happend on the release branch, i.e. CHANGELOG and manifest updates are also present on the dev branch.
 
       # if needed, you can checkout the latest master here, build artifacts and publish / deploy them somewhere