test: run on Python 3.11 as well

Author: László Vaskó

.github/workflows/main.yml

@@ -52,7 +52,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
     steps:
       - name: Checkout source code
         uses: actions/checkout@v2