ci: Test against Python 3.14 freethreaded build

Author: auscompgeek

.github/workflows/dist.yml

@@ -98,6 +98,7 @@ jobs:
         - '3.12'
         - '3.13'
         - '3.14-dev'
+        - '3.14t-dev'
         exclude:
         - os: macos-14
           python_version: '3.8'