Update reveal.js to 4.x

[pganssle]

There are a number of breaking changes, most of which are documented here: https://revealjs.com/upgrading/

This may not work properly with reveal.js dependencies, since this does not try to upgrade these to use the new plugins mechanism.

[mrmanc]

Thanks for this and apologies that I’ve not looked at it yet. I’m interested in getting things updated, but I find that this update breaks the rendering of the fragments slide. I can’t quite work out why, but the final fragment in the page appears when the slide loads, and there seems to be a phantom fragment before the first one in the page. I’m guessing something nuanced has changed over how reveal.js works with the element classes, but I’m not sure how. I expect this is going to cause a breaking change to existing slides as a result.

If we can understand and fix the rendering, I expect this will be a major release for these reasons.

[mrmanc]

As a note, I believe anyone wishing to change to this will need to cd reveal.js && git checkout 4.0.2 in order to update the submodule. There’s probably a simpler way to pull that change as part of pulling the repo, but it caught me out.

[Sieboldianus]

Many thanks! Tested this and everything works, except data-background-image elements won't render. I'll add information once I found the reason.

[edit] This was my fault, I used "image/link" instead of without quotes. Everything works.

[Sieboldianus]

Thank you! The suggested edits worked flawlessly for me for reveal 4.4.0. I also added a number of hooks to support new functions:

| replace:'<slide-id>','<!-- .slide: id="'
| replace:'</slide-id>','" --> '
| replace:'<slidevisibility>','<!-- .slide: data-visibility="'
| replace:'</slidevisibility>','" --> '
| replace:'<auto-animate/>','<!-- .slide: data-auto-animate -->'