Add py311 to CI

Author: nvictus

.github/workflows/pytest.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ '3.9', '3.10', '3.12' ]
+        python-version: [ '3.9', '3.10', '3.11', '3.12' ]
 
     steps:
     - uses: actions/checkout@v2