Setting up matrix for Python version testing

.github/workflows/example.yml

@@ -5,12 +5,16 @@ on:
 jobs:
   plastex:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+
     steps:
       # for now, because callable has changed
-      - name: Use older Python version
+      - name: Setup Python ${{ matrix.python-version }}
         uses: actions/setup-python@v4
         with:
-          python-version: "3.9"
+          python-version: ${{ matrix.python-version }}
       - name: Install TeXLive
         uses: teatimeguest/setup-texlive-action@v2
         with: