Automatically merge the release branch into main and push it.

Author: nedtwigg

.github/workflows/deploy.yml

@@ -66,3 +66,6 @@ jobs:
         if: "${{ github.event.inputs.to_publish == 'lib' }}"
         run: |
           ./gradlew :changelogPush -Prelease=true --stacktrace --warning-mode all --no-configuration-cache
+      - run: git checkout main
+      - run: git merge release --ff-only
+      - run: git push origin main