Test on py 3.13

Author: pgleeson

.github/workflows/ci_versions.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
         runs-on: [ubuntu-latest, macos-latest, ubuntu-24.04 ]
         exclude:
           - runs-on: macos-latest