Add python 3.12 support classifier to pypi

Author: Archmonger

setup.py

@@ -42,6 +42,7 @@
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
+        "Programming Language :: Python :: 3.12",
         "Topic :: Software Development :: User Interfaces",
         "Topic :: Software Development :: Widget Sets",
         "Typing :: Typed",