delete all previews on merge or close

.github/workflows/cleanup-preview.yml

@@ -0,0 +1,27 @@
+name: Cleanup PR Preview
+
+on:
+  pull_request:
+    types: [closed]
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup SSH
+        run: |
+          mkdir -p ~/.ssh
+          echo "${{ secrets.GH_PAGES_DEPLOY_KEY }}" > ~/.ssh/id_rsa
+          chmod 600 ~/.ssh/id_rsa
+          ssh-keyscan github.com >> ~/.ssh/known_hosts
+
+      - name: Delete All Previews
+        run: |
+          git clone --single-branch --branch gh-pages [email protected]:MHKiT-Software/MHKiT.git gh-pages
+          cd gh-pages
+          rm -rf pr-previews/
+          git config user.name "GitHub Actions Bot"
+          git config user.email "<>"
+          git add -A
+          git commit -m "Remove all previews after merging PR #${{ github.event.pull_request.number }}" || echo "No cleanup needed"
+          git push