feat: add workflow to delete merged branch (#10314)

* Create delete-branch.yml

* Update delete-branch.yml

* Update delete-branch.yml

.github/workflows/delete-branch.yml

@@ -0,0 +1,22 @@
+name: Delete merged branch
+on:
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  delete-branch:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    if: github.event.pull_request.merged == true && github.event.pull_request.head.repo.full_name == github.repository
+    steps:
+      - name: Delete merged branch
+        uses: actions/github-script@v7
+        with:
+          script: |
+            github.rest.git.deleteRef({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              ref: `heads/${context.payload.pull_request.head.ref}`,
+            })