Advertize and test Python 3.11 support

Change-Id: Ic1d5aaaf8043e4c1c732b37410a88e5b22e54b44
diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index 9bca603..59b42cb 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -10,7 +10,7 @@
       max-parallel: 6
       fail-fast: false
       matrix:
-        python-version: ['3.9', '3.10']
+        python-version: ['3.9', '3.10', '3.11']
         r-version: [release]
         os: [windows-latest, macOS-latest, ubuntu-latest]
     steps: