Start testing on Python 3.13 (#1122)

Python 3.13 is currently in alpha, but it's useful to have a
test scenario to vet it early before it is released to flush
out any Bandit issues as a result of a new runtime.

Signed-off-by: Eric Brown <eric_wade_brown@yahoo.com>

.github/workflows/pythonpackage.yml

@@ -52,6 +52,7 @@ jobs:
           ["3.10", "310"],
           ["3.11", "311"],
           ["3.12", "312"],
+          ["3.13.0-a - 3.13", "313"],
         ]
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}