Add version checks for Blurb and Sphinx in workflow

Author: rffontenelle

.github/workflows/check.yml

@@ -73,6 +73,9 @@ jobs:
       - name: Add problem matcher
         uses: sphinx-doc/github-problem-matcher@v1.1
 
+      - run: cpython/Doc/venv/bin/blurb help
+      - run: cpython/Doc/venv/bin/sphinx-build --version
+      
       - name: Build docs
         id: build
         run: ./scripts/build.sh ${{ matrix.format }}