ci: Prepend to changelog on (pre)release (#784)

Author: janbuchar

.github/workflows/pre_release.yaml

@@ -27,6 +27,7 @@ jobs:
         name: Prepare release metadata
         with:
           release_type: prerelease
+          existing_changelog_path: CHANGELOG.md
 
   # If github.ref points to a [ci skip] commit, this workflow won't run.
   # Otherwise, these checks will be launched from the `run_code_checks` workflow.

.github/workflows/release.yaml

@@ -41,6 +41,7 @@ jobs:
         with:
           release_type: ${{ inputs.release_type }}
           custom_version: ${{ inputs.custom_version }}
+          existing_changelog_path: CHANGELOG.md
 
   # If github.ref points to a [ci skip] commit, we assume that it was added by the pre_release workflow, 
   # which doesn't push the commit if code checks don't pass.