adding dependencies for doc testing

.github/workflows/testing.yml

@@ -12,6 +12,10 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
+    - name: Setup Node
+        uses: actions/setup-node@v1
+        with:
+          node-version: '12'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip