[Feature] Admin option (or per-gist option) to display automatic table of contents of files in gist

[alyssadev]

Admittedly a feature that github gist doesn't have so might be out of scope.
On gists with more than one (or two or three) file(s), show an expandable table of contents below the description, or perhaps in one of the margins, letting users quickly jump past files. I've been adding a "_index.md" file to gists to accomplish this but would be nice to have this automated.

Related features: collapsible files, markdown table of contents support