The GitHub wiki (Gollum derived) supports multiple wiki page formats.

You can use the Mediawiki __TOC__ directive to create a page table of contents. (Whole wiki table of contents, probably not.)

None pf the other wiki page formats have this ability :-(.

Table of Contents Level 1 Level 2 Level 3 Level 4 Level 5 Level 6

directive in a GitHub wiki page.