Add pypandoc-binary requirement to tox setup

Author: mmore500

.github/workflows/CI.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          python -m pip install tox tox-gh-actions
+          python -m pip install tox tox-gh-actions pypandoc-binary
 
       # Install TeX distribution for PGF output from matplotlib
       - name: Install TeX distribution for PGF output (Ubuntu)