Add python 3.13 to test matrix.

Author: mikaelfrykholm

.github/workflows/python-package.yml

@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-24.04", "ubuntu-22.04", "ubuntu-20.04"]
-        python: ["3.9", "3.10", "3.11", "3.12"]
+        python: ["3.9", "3.10", "3.11", "3.12", "3.13"]
     runs-on:  ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v4