tests: add more Python versions (#49)

- 3.12
- 3.13
- 3.14

Author: sgaist

.github/workflows/workflow.yml

@@ -37,10 +37,18 @@ jobs:
           - "3.9"
           - "3.10"
           - "3.11"
+          - "3.12"
+          - "3.13"
+          - "3.14"
         jupyterhub-version:
           - "3"
           - "4"
           - "5"
+        exclude:
+          - python-version: "3.13"
+            jupyterhub-version: "3"
+          - python-version: "3.14"
+            jupyterhub-version: "3"
 
     steps:
       - uses: actions/checkout@v6