run unit tests on the latest python version 3.11

Author: MalteKurz

.github/workflows/pytest.yml

@@ -29,6 +29,7 @@ jobs:
           - {os: 'macOS-latest', python-version: '3.8'}
           - {os: 'ubuntu-latest', python-version: '3.9'}
           - {os: 'ubuntu-latest', python-version: '3.10'}
+          - {os: 'ubuntu-latest', python-version: '3.11'}
 
     steps:
     - uses: actions/checkout@v2