Add 3.13 to basepython (#3589)

Author: sentrivana

tox.ini

@@ -766,6 +766,7 @@ basepython =
     py3.10: python3.10
     py3.11: python3.11
     py3.12: python3.12
+    py3.13: python3.13
 
     # Python version is pinned here because flake8 actually behaves differently
     # depending on which version is used. You can patch this out to point to