define py version numbers as str, not num

Author: lissensp

.github/workflows/test.yaml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-python@v2