Add Python 3.13 to CI matrix for testing

Author: bhimrazy

.github/workflows/ci-testing.yml

@@ -23,7 +23,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: ["3.10", "3.11", "3.12"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
         include:
           - { os: "ubuntu-22.04", python-version: "3.10", requires: "oldest" }