ci: Add GH workflow to build app & deploy to GH Pages; Update demo link to point at GH Pages deployment.

.github/workflows/deploy-gh-pages.yml

@@ -0,0 +1,38 @@
+name: "Deploy to GitHub Pages"
+
+on:
+  push:
+    branches: [ "main" ]
+
+jobs:
+  build:
+    runs-on: "ubuntu-latest"
+
+    steps:
+    - uses: "actions/checkout@v4"
+
+    - name: "Set up Node.js"
+      uses: "actions/setup-node@v4"
+      with:
+        node-version: "22"
+
+    - run: "npm install"
+    - run: "npm run build"
+
+    - name: "Upload static files as artifact"
+      uses: "actions/upload-pages-artifact@v3"
+      with:
+        path: "./dist"
+
+  deploy:
+    needs: "build"
+    permissions:
+      pages: "write"     # to deploy to Pages
+      id-token: "write"  # to verify the deployment originates from an app
+    runs-on: "ubuntu-latest"
+    environment:
+      name: "github-pages"
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        uses: actions/deploy-pages@v4