Coveralls, multiple python versions

- Tox requires you to pre-install the Python interpreters
- Coveralls needs a program to be installed

.github/workflows/run-tests.yml

@@ -11,13 +11,16 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.10"
+          python-version: |
+              '3.9'
+              '3.10'
+              '3.12'
 
       - name: Install dependencies
         run: |
           sudo apt-get install libblas-dev liblapack-dev libxc-dev
           python -m pip install --upgrade pip
-          python -m pip install tox
+          python -m pip install tox coveralls
 
       - name: Test with tox / unittest / coverage
         run: |