Test on Python 3.13

Author: spookylukey

tox.ini

@@ -1,7 +1,7 @@
 # This config is for local testing. Where needed changes should be duplicated into
 # .github/workflows/pythonpackage.yml
 [tox]
-envlist = py38,py39,py310,py311,py312
+envlist = py38,py39,py310,py311,py312,py313
 
 [testenv]
 commands = pytest {posargs}