Document `\QuartoMarkdownBase64` in general documentation

[cderv]

This currently still documented as a 1.4 highlight only

• https://quarto.org/docs/prerelease/1.4/ast.html#include-quarto-markdown-in-latex-raw-blocks

It should be put either in Table part or elsewhere in PDF part.

---

(about data-qmd attribute for HTML table)

This mechanism only exists for HTML at the moment.

And we have another hole in our documentation !! In 1.4, we introduced similar command for raw LaTeX table : https://quarto.org/docs/prerelease/1.4/ast.html#include-quarto-markdown-in-latex-raw-blocks

There is a special command to use: \QuartoMarkdownBase64{<<base64-encoded-markdown-content>>}

However, this is currently not working for Citations key as resolving citation requires more context that just render some Markdown inside LaTeX table

• QuartoMarkdownBase64 works with cross references but not citation keys in LaTeX/PDF #9342

Originally posted by @cderv in #13455 (reply in thread)