Add 3.11 to AppVeyor

Author: hugovk

appveyor.yml

@@ -15,6 +15,7 @@ environment:
     - PYTHON: "C:\\Python38-x64"
     - PYTHON: "C:\\Python39-x64"
     - PYTHON: "C:\\Python310-x64"
+    - PYTHON: "C:\\Python311-x64"
 
 install:
   # Newer setuptools is needed for proper support of pyproject.toml