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.

.gitlab-ci.yml

@@ -53,7 +53,7 @@ test:
 
   artifacts:
     paths:
-      - /tmp/pytest-of-root/pytest-0/test_plot_attention0/*
+      - /tmp/pytest-of-root/pytest-0/test_plot_attention0/0a56e8b3-95cd-4fa5-a17b-5b0ff9e6ea84_line.gif
     expire_in: 1 day
 
 docker-build: