Add Python 3.13 to the testing

Author: cclauss

.github/workflows/run_tests.yml

@@ -5,14 +5,15 @@ jobs:
   build:
     runs-on: ubuntu-latest
     strategy:
-      max-parallel: 5
+      max-parallel: 6
       matrix:
         python-version:
           - "3.8"
           - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
+          - "3.13"
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-python@v5