Update revealjs v5 and dependencies

[cderv]

Towards

• Update Revealjs to latest version 5 #4795

• Revealjs 5.1.0, new JS and themes

• Reveal Plugins 4.2.5 for chalkboard 2.3.3

This PR includes docs and process to update revealjs theming. It helps understand how this currently works to maps Sass variables from user's theming, to quarto internals, and then to expected Reveal.js own SASS theming system.

We probably need more tests as most of the change will have effect in browser running JS code for reveal, so we don't have much test with this yet.

Manual testing

• Demo slides: https://quarto.org/docs/presentations/revealjs/demo/ - Works OK !
• All simpler demo examples from: https://quarto.org/docs/presentations/revealjs/demo/mini - Works OK !
• All examples from https://quarto.org/docs/presentations/revealjs/examples - Works OK !
• Checking all the themes change - I made a website to help with this : https://cderv.github.io/quarto-revealjs-themes/

[cscheid]

This looks great!

Keeping in mind the upcoming posit::conf presentations, we should either:

• merge ASAP (as in today), or
• merge the day after posit::conf is done

What do you think?

[cderv]

😄 definitely the main question. I ask myself the same, hence the draft state. We have a stable release working we could also consider that anyone doing a presentation for "production" (posit::conf) would use a stable version and not a pre-release 😉 Though our users likes to live on the edge of new stuff ! 😆

I don't think the effect if big, but we don't really have test regarding how feature works in in a live browser situation so it requires manual testing. And I am just starting them.

Could be small or no effect, but could also be the opposite 🤷‍♂️. So considering the milestone of conf, we should probably let this in a branch. This also leave me time to add to this, rebasing often on main and adding some tests.

What is your take on this ?

[cscheid]

You have the hands-on experience.

So considering the milestone of conf, we should probably let this in a branch.

That works for me. Let's plan to merge right after conf.

[cderv]

Nevermind, it seems it is fixed upstream:

• fix: disable revealjs' backdrop filter on overlays rajgoel/reveal.js-plugins#180

We need an unreleased version of chalkboard.

[cderv]

Very small theme change after all, and it is now more inline with revealjs own theme.

All good to merge this PR so I'll go ahead.

I'll update documentation for 1.6 to close #4795 , including adding an highlight