Add hugo-md to pandoc-all in format-aliases.yml

[cderv]

The hugo-md format is defined as a Quarto extension at src/resources/extensions/quarto/hugo/_extension.yml (based on md with variant: gfm+yaml_metadata_block+definition_lists+smart), but it is not listed in pandoc-all in format-aliases.yml.

This causes quarto-web's tools/reference.ts to produce an empty hugo.json for the format reference page. The script derives format names from .qmd filenames and checks each option's resolved format list against pandoc-all. Since hugo / hugo-md is not in that list, no options match.

The dashboard format was handled by adding it as a synthesized format in pandoc-all. The same approach would work for hugo-md.

There is also a naming mismatch to consider: the extension defines the format as hugo-md, but the quarto-web reference page uses hugo.qmd (deriving the name hugo). The upstream fix should clarify which name should be canonical.

quarto-web has a workaround (mapping hugo to gfm for option lookup) but the proper fix belongs here.