Add Python 3.14t (freethreaded) to testing matrix

- Added Python 3.14t to the test matrix
- Python 3.14.0 freethreaded is available on all platforms (Ubuntu, Windows, macOS)
- Tests will run on all supported OS and architectures

Author: vinitkumar

.github/workflows/pythonpackage.yml

@@ -28,7 +28,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [pypy-3.10, pypy-3.11, '3.10', '3.11', '3.12', '3.13', '3.14']
+        python-version: [pypy-3.10, pypy-3.11, '3.10', '3.11', '3.12', '3.13', '3.14', '3.14t']
         os: [
           ubuntu-latest,
           windows-latest,