Upload index.html as artifact

Author: hugovk

.github/workflows/update.yml

@@ -27,3 +27,7 @@ jobs:
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           branch: ${{ github.ref }}
+      - uses: actions/upload-artifact@v4
+        with:
+          name: index.html
+          path: index.html