A real major version

[Mister-Hope]

Hi there, I am a big fun of reveal.js. I just saw v5 release for reveal.js, however it's not containing the changes I wanted.

1. Reveal.js still uses marked v4, which has known bug unfixed. (markdown plugin) Suggesting upgrading to latest v9

2. The plugins are bundled by an old version rollup@v2 while rollup@v4 already released. We can update our packing pipline.

3. It's time for dev env update. Since node v20 is already LTS, can we bump all non-major deps and limit our dev env to Node.js18+ (or even node 20 only)?

4. All deps versions can be lifted to the latest major.

5. Since reveal.js already has a well type package @types/reveal.js I think we can try to make types built-in, (I can take the maintaining job, just mention me in prs with any api changes)

   BTW, I am trying to create a pr to improve @types/reveal.js as well

6. The whole community is moving to ESM, so we can update reveal.js to be full ESM ready in a major release.

If you want, those pr can be created and sent to you shortly, where we can move on to v6 quickly to get "a real major version"