docs: official support for Python 3.12 and 3.13

Author: jpgrayson

setup.cfg

@@ -25,6 +25,8 @@ classifiers =
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
+    Programming Language :: Python :: 3.12
+    Programming Language :: Python :: 3.13
     Programming Language :: Python :: Implementation :: CPython
     Programming Language :: Python :: Implementation :: PyPy
     Topic :: Scientific/Engineering