Add CI checks on free-threaded Python 3.14 #412

Job	Run time
Build wheels for ARM64 on Windows	17m 19s
Build ubuntu-22.04 (x86_64) wheels	5m 37s
Build source distribution	41s
Build ubuntu-24.04-arm (aarch64) wheels	8m 5s
Build wheels for AMD64 on windows-latest	13m 17s
Build wheels for arm64 on macos-14	7m 20s
Build wheels for x86_64 on macos-15-intel	11m 13s
Show artifacts	7s
Publish to PyPI	0s
	1h 3m 39s

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