Add support for slideshows using sphinx-carousel

sphinx-carousel is a Sphinx extension for creating slideshows using Bootstrap carousels. The extension supports the PyData Sphinx theme that we are currently using.

This would be a nice addition to show the various steps of an algorithm in swh-alter documentation.

See: https://sphinx-carousel.readthedocs.io/ and https://getbootstrap.com/docs/5.1/components/carousel/

swh/docs/sphinx/conf.py

@@ -42,6 +42,7 @@ extensions = [
     # swh.scheduler inherits some attribute descriptions from celery that use
     # custom crossrefs (eg. :setting:`task_ignore_result`)
     "sphinx_celery.setting_crossref",
+    "sphinx_carousel.carousel",
     "sphinx_design",
 ]