Add Python 3.14 to test matrix

Author: Lauszus

.github/workflows/pythonpackage.yml

@@ -9,7 +9,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: [
-          '3.9', '3.10', '3.11', '3.12', '3.13',
+          '3.9', '3.10', '3.11', '3.12', '3.13', '3.14',
           'pypy-3.9', 'pypy-3.10', 'pypy-3.11'
         ]
     steps: