Add Python 3.13 classifier to devel branch

Author: Shrews

setup.cfg

@@ -22,6 +22,7 @@ classifiers =
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3.12
+    Programming Language :: Python :: 3.13
     Programming Language :: Python :: 3 :: Only
     Topic :: Software Development :: Libraries :: Python Modules
     Topic :: System :: Systems Administration