build: add Python 3.13 to setup.cfg

Author: sg495

pypi-distrib-upload.bat

@@ -1,3 +1,3 @@
-python -m build
-python -m twine upload --skip-existing dist/*
+python312 -m build
+python312 -m twine upload --skip-existing dist/*
 pause

setup.cfg

@@ -15,6 +15,7 @@ project_urls =
 # see https://pypi.org/classifiers/
 classifiers =
     Development Status :: 4 - Beta
+    Programming Language :: Python :: 3.13
     Programming Language :: Python :: 3.12
     Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3.10