ci: fix release pipeline, add permissions to GH token

Author: dgniewek

.github/workflows/prepare-release.yml

@@ -6,11 +6,13 @@ on:
       version_part:
         description: The part of the version to update (patch, minor or major)
         required: true
-        default: 'minor'
+        default: "minor"
 
 jobs:
   prepare-release:
     runs-on: ubuntu-latest
+    permissions:
+      contents: write # to create branch, tag and push the changes
     strategy:
       matrix:
         python-version: [3.9]
@@ -26,7 +28,7 @@ jobs:
         run: |
           echo "INPUT_VERSION_PART: ${{ github.event.inputs.version_part }}"
           python -c "if '${{ github.event.inputs.version_part }}' not in ['patch', 'minor', 'major']:   raise ValueError(\"'${{ github.event.inputs.version_part }}' must be one of ['patch', 'minor', 'major'])\")"
-      - name: Bump the version number  # bump2version is a maintained fork of original bumpversion
+      - name: Bump the version number # bump2version is a maintained fork of original bumpversion
         id: bump_version
         run: |
           pip install bump2version