Add support for Python 3.12

Closes #314 (closed)

Refs https://gitlab.teklia.com/workers/dan/-/merge_requests/197

I introduced the threshold on the attention GIF comparison because, for some reason, there was a small difference in CI but not reproducible locally.

tests/test_attention.py

@@ -36,7 +36,7 @@ def _compare_gifs(reference: Path, hypothesis: Path) -> bool:
         zip(ImageSequence.Iterator(im1), ImageSequence.Iterator(im2))
     ):
         # True if there is a difference, False if they are identical
-        has_diff = ImageChops.difference(ref_frame, hyp_frame).getbbox()
+        has_diff = np.asarray(ImageChops.difference(ref_frame, hyp_frame).getbbox()).mean() > 0.05
         if has_diff:
             print(idx, np.asarray(ImageChops.difference(ref_frame, hyp_frame)).mean())
         identical &= not has_diff