Proposal: Use furo theme for Sphinx docs

[securitykernel]

We currently use the readthedocs theme for publishing documentation on https://botan.randombit.net with Sphinx.

I recently discovered the furo theme for Sphinx, which is used by pip, python-gitlab, urllib3 and more. IMHO it looks much cleaner than readthedocs, and optionally allows the user to switch to dark mode. Below are some screenshots for comparison. I also uploaded a full recent Botan docs made with furo to https://docs.botan-crypto.org/furo/ to browse.

Start page

Building The Library

Random Number Generators

TLS Code Example

What do you think?

[randombit]

No objection here

[mouse07410]

Does this add a dependency and require installing an extra Sphinx theme furo?

If so, shouldn't building.md tell that it's necessary for docs target, and how to install it?

[securitykernel]

It is not required. Just like before with the readthedocs theme, it will fall back to the agogo theme shipped with Sphinx automatically if furo is not found.

[lieser]

@randombit I would love it if the official Botan website could switch to this theme. Currently it is only used as the default in the build scripts (if available), but not on the official site.

I think long sites like e.g. https://botan.randombit.net/handbook/api_ref/pubkey.html would benefit a lot of the better navigation via the sidebar that duro provides compared to the theme currently used.