Support Dark Mode for Pytest Docs Website

[cverrier]

What's the problem this feature will solve?

Reading the documentation in the evening can be quite uncomfortable due to the current (very bright) theme of the docs website.

Describe the solution you'd like

Having the option to turn on/off a dark theme for the docs website.

[The-Compiler]

We use the Pallets Sphinx theme which doesn't seem to offer a dark mode.

It looks like even Pallets has plans to switch to Furo which does.

Maybe we should reevaluate #6402 (where we ended up upgrading our theme to upstream Pallets in #6453) and instead adopt Furo? I'd be +1 on that.

[nicoddemus]

👍 from me too, however I probably won't have time to work on this, but would be happy to review the work if someone does tackle this.

[jiaweikho]

👍 I'm all for dark mode docs everywhere. I'd like to have a go at this, though I suspect a switch to Furo might mean a few design changes to the site. It would be useful to use this issue to discuss the design if it's the right forum to do so.

[samjirovec]

Hey all, I took some time to do a quick conversion from Flask to Furo. Only big design change was with the side-nav turning into a note + the main side-nav now being scrollable.

https://github.com/pytest-dev/pytest/pull/12326

[cverrier]

Thanks a lot @samjirovec, I tried the dark mode and it looks really good! :rocket:

Since this feature has already been merged with commit cbf6bd9, I will close this issue.