chore: add GitHub Pages deployment workflow for demo

.github/workflows/pages.yml

@@ -0,0 +1,54 @@
+name: Deploy Demo to GitHub Pages
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Only allow one concurrent deployment
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build demo
+        run: |
+          npx ng build demo \
+            --configuration production \
+            --base-href /grapesjs-angular/
+
+      - name: Upload Pages artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: dist/demo/browser
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4