setup.py: add Python 3.11 classifier

setup.py

@@ -28,6 +28,7 @@ setup(
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.11",
 
         "Intended Audience :: Developers",
         "Intended Audience :: Customer Service",