add Python 3.13t support

[electroglyph]

I haven't been using Fastembed lately, but decided to replace my little ONNX wrapper with Fastembed just to tidy it up.

that's when I noticed that Fastembed silently dies on import in Python 3.13t, so here's the fix I'm currently using.

this PR:

• moves Fastembed closer to Python 3.13t compatibility

• updates pyo3 dependency to support Python 3.13t

• slightly updates Rust code

• updates (unused?) test

tested on Python 3.12 and Python 3.13.3+ free-threaded.

closes #4

edit: I haven't tested the workflow, but I looked at the Github actions before I updated the workflow, and my changes should be fine.

[electroglyph]

there's an open PR (huggingface/tokenizers#1774) for tokenizers which adds 3.13t support. after that gets merged this PR will make fastembed 3.13t compatible

[ArthurZucker]

Merged!

[terencehonles]

This looks like this is the cause of a segfault on Python 3.14 (a default build), or at least pulling in this PR does not segfault compared to the latest commit on master 8db3c14.