Add CI/CD workflow for cleaning up closed pull requests (#2)

Author: daniel-richter

.github/workflows/build-cleanup.yaml

@@ -0,0 +1,24 @@
+name: CI/CD (Clean up)
+
+on:
+  pull_request:
+    types: [closed]
+  workflow_dispatch: ~
+
+env:
+  SOURCE_BRANCH: ${{ github.head_ref || github.ref_name }}
+  RELEASE_BRANCH: "release/${{ github.head_ref || github.ref_name }}"
+
+jobs:
+  clean-up:
+    name: Clean up
+    runs-on: [ubuntu-latest]
+    steps:
+      - uses: actions/github-script@v7
+        with:
+          script: |
+            github.rest.git.deleteRef({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              ref: "heads/${{ env.RELEASE_BRANCH }}",
+            });