Add group for options that need Typst specific content in docs

[cwickham]

1. Adds typst to the document groups in groups.yml so that document-typst.yml options (logo, margin-geometry, theorem-appearance) are included when generating format reference pages.

   Without this, the typst-specific options defined in document-typst.yml were never read by tools/reference.ts in quarto-web, so they didn't appear on the typst reference page.

2. Moves the typst margin definition from document-reveal-layout.yml to document-layout.yml, resulting in two separate declarations of margin. This pattern already exists for several other options in the schema so I'm hoping it doesn't cause problems.

   @gordonwoodhull could you double-check the Typst schema for margin Claude proposed here?

Fix for #13412

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[cderv]

Awesome thank you !!

Why Partial fix only ?

I think this + the reference update covers it right ?

[cwickham]

@cderv we still have a Slide Layout section on the typst page:

I'll add something to this PR for that shortly.

[cwickham]

@cderv this should now close #13412. It's a bigger change, so please review the edited description. I've also tagged @gordonwoodhull for a review, particularly on the margin schema for typst.