RefTargets: Float

[cscheid]

This is step 1 of #4944.

Crossreferenceable "floats" can now be targeted directly in Lua under the FloatRefTarget custom AST name, and work more generically than our previous system.

There's more to be done in this branch (notably, typst support), but I want to start running the test suite.

Known issues:

• the acm-pdf failure is to be expected, and will need changes in that format template.

My TODOs:

• Things that we can handle post-merge:
  • Audit attrs.yml with new features (discuss with @jjallaire how to do this for custom categories)
    • Put the custom categories resolution into the output of quarto inspect
  • What should we do with figure labels that now point to an invalid crossref category, like plot-dot in tests/docs/smoke-all/2023/01/05/plots.ipynb?
• Redo flags.lua with new filter organization
• Clean up file organization a bit
• Address FIXMEs in code
• Are we testing Epub crossrefs right now?
  • run output through epubcheck
• Subfloats for Typst format
• Changelog
• Documentation (on https://github.com/quarto-dev/quarto-web/tree/feature/float-reftargets until this merges)
• Ensure https://github.com/quarto-dev/quarto-web builds correctly

  • Test other sites from https://quarto.org/docs/gallery/

    Observation: gallery sites are often built once and no longer updated, which is a problem for us both ways. 1) the documents might no longer build and 2) the documents might no longer have to be built. The idea of watching GHA workflows is probably more fruitful.

    • https://github.com/mikemahoney218/mm218.dev