Incorporate panel sets

[coatless]

Thanks to cscheid's response: https://github.com/quarto-dev/quarto-cli/discussions/9646#discussioncomment-9451134

There's now a way forward to accomplishing:

1. showcasing what options are being used so we're not copying and pasting on the custom cell
2. offering rendered results alongside the interactive cell (c.f. https://github.com/quarto-dev/quarto-cli/discussions/4761#discussioncomment-5338441)

With this work out of the way, we can move to incorporating it inside of altdoc.

[coatless]

quarto-panelize is now available:

https://github.com/coatless-quarto/panelize

We probably should add a documentation entry describing its use.

Ditto with adding a new entry showing an application with altdoc to create package websites with interactive examples.

https://github.com/coatless-r-n-d/quarto-webr-in-altdoc