Update furo requirement from >=2023.09.10 to >=2025.12.19

[dependabot]

Updates the requirements on furo to permit the latest version.

Release notes

Sourced from furo's releases.

2025.12.19

• Bump the supported Sphinx version range

Full Changelog: pradyunsg/furo@2025.09.25...2025.12.19

Changelog

Sourced from furo's changelog.

2025.12.19 -- Harmonious Honeydew

• ✨ Add support for Sphinx 9.
• Drop support for Sphinx 6.

2025.09.25 -- Gleaming Green

• Change the dark mode code back to native.

2025.07.19 -- Frozen Flame

• ✨ Switch to accessible-pygments themes
• ✨ Prefetch the sidebar logos
• ✨ Fix flickering header drop shadow on Safari
• Add rel=edit attribute to "Edit this page" link/icon
• Bump NodeJS and npm dependency versions
• Bump Saas & Webpack major versions
• Improve current page detection to be resilient to sticky elements above header
• Modernise Sass and use @use + @forward
• Remove top of code border-radius with captions
• Remove "debug printf" for headerTop value
• Use distinct images for light and dark mode in the documentation
• Use the modern Saas Modules

2024.08.06 -- Energetic Eminence

• ✨ Add support for Sphinx 8
• ✨ Add smoother transitions between breakpoints
• Increase specificity of table-wrapper selector
• Avoid page breaks inside paragraphs

2024.07.18 -- Dull Denim

• Improve how icons are handled and aligned.
• Improve scroll event handler.
• Hide the copybutton by default.
• Fix source_view_link configuration handling.
• Fix close tag on pencil icon.

2024.05.06 -- Cheerful Cerulean

• ✨ Add new custom icons for auto mode, reflecting the currently active theme.
• ✨ Add a view this page button.
• ✨ Add colours and highlighting to "version modified" API helpers.
• ✨ Add release information to various customisation knobs.
• Make all icons bigger and use a thinner stroke with them.

2024.04.27 -- Bold Burgundy

• Add a skip to content link.

... (truncated)

Commits

• dd9e9f9 Prepare release: 2025.12.19
• d43f7e9 Update changelog
• d27cab5 Bump the supported Sphinx version range
• 12f288e Back to development
• 7c5f8fa Prepare release: 2025.09.25
• 8bfdc54 Update changelog
• d92b62f Switch the dark mode theme back to native
• 83c3446 Add Blender to "used by" section (#898)
• 426ea05 Remove old scrollbar selectors (#892)
• d22d31c Remove trailing slash on void elements (#895)
• Additional commits viewable in compare view