Pin minimum version of furo to 2024.8.6 (#64)

Fix incompatibility with sphinx=8.0 causing `AttributeError: _CascadingStyleSheet is immutable` with old versions of furo.

Author: weiji14

ci/doc.yml

@@ -12,7 +12,7 @@ dependencies:
   - ipython
   - ipykernel
   - ipywidgets
-  - furo
+  - furo>=2024.8.6
   - myst-nb
   - xarray
   - pip: