Add missing identifier for Python 3.12 support

Author: jobovy

setup.py

@@ -317,6 +317,7 @@ def build_extensions(self):
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
+        "Programming Language :: Python :: 3.12",
         "Environment :: WebAssembly :: Emscripten",
         "Topic :: Scientific/Engineering :: Astronomy",
         "Topic :: Scientific/Engineering :: Physics",