Update Python version matrix in GitHub Actions workflow to include 3.13

Author: KenMwaura1

.github/workflows/pythonapp.yml

@@ -13,7 +13,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.9, "3.10", "3.11", "3.12"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
+        # Including Python 3.10 (LTS until 2026) and latest stable versions
+        # GitHub Actions automatically gets the latest patch versions
 
     steps:
       - uses: actions/checkout@v5