Install jupyterlab-widgets for the GitHub Pages deployment (#27)

Author: jtpio

.github/workflows/build.yml

@@ -109,7 +109,7 @@ jobs:
           name: extension-artifacts
       - name: Install the dependencies
         run: |
-          python -m pip install --pre jupyterlite-core jupyter-server jupyterlite_javascript_kernel*.whl
+          python -m pip install --pre jupyterlite-core jupyter-server jupyterlab-widgets jupyterlite_javascript_kernel*.whl
       - name: Build the JupyterLite site
         run: |
           jupyter lite build --output-dir dist --contents examples