See the GitHub blog post Footnotes now supported in Markdown fields. Here is the HN discussion. I verified that GitHub’s web interface renders and links footnotes in README.md files or any other .md file in a repo. As of this writing the published GFM spec hasn’t been updated to reflect this. But the support added to cmark.gfm has been published: Changes since last release (0.29.0.gfm.1...0.29.0.gfm.2): Fixed issues with footnote rendering when used with the autolinker (#121), and when fo...
