github action added to build sphinx-based doc.

.github/workflows/documentation.yaml

@@ -14,6 +14,8 @@ jobs:
       - uses: actions/setup-python@v3
       - name: Install dependencies
         run: |
+          echo "project dir is '${BME_PROJECT_DIR}'"
+          pip --version
           pip install -r python-virtualenvs/multigit-development.requirements
       - name: Sphinx build
         run: |