use container image

.github/workflows/main.yml

@@ -9,6 +9,8 @@ on:
 jobs:
   test:
     runs-on: ubuntu-22.04
+    container:
+      image: ghcr.io/mxmehl/python-tests-image:3.12
     steps:
       - name: Checkout
         uses: actions/checkout@v4