CI: provide binary wheels for free-threaded CPython

[hombit]

The support for free-threading CPython interpreters is coming with PR #499

Currently, there is no ABI3-compatibility for the free-threaded versions of CPython, so if we want to release binary wheels, they would be version-specific. This would make binary wheel storage on PyPI grow fast, and I'm concerned about reaching the quota.

Please let me know in the comments if you need the free-threaded binary wheels, and we can work on releasing them.