Fix sphinx markdown tables (jupyterlab-contrib#35)

Author: fcollonval

.github/workflows/pages.yml

@@ -18,7 +18,7 @@ jobs:
           python-version: "3.9"
           architecture: "x64"
       - name: Install dependencies
-        run: python -m pip install sphinx sphinx-material recommonmark sphinx-markdown-tables requests pytest-check-links
+        run: python -m pip install sphinx sphinx-material recommonmark git+https://github.com/Dzordzu/sphinx-markdown-tables@3bc0849cf6dc0e1b7fe52aafadc2e2ccca698a01 requests pytest-check-links
       - name: Check links
         run: |
           cp extensions.tpl extensions.md