x/pkgsite: add support for github's markdown footnotes

[madkins23]

What is the URL of the page with the issue?

https://pkg.go.dev/github.com/madkins23/go-slog@v0.8.3-alpha-server/infra#section-readme

What is your user agent?

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Screenshot

Github:

pkg.go.dev:

What did you do?

Added footnotes to README.md file per Github markdown syntax.

What did you see happen?

Works fine in Github. Footnotes not respected in pkg.go.dev.

What did you expect to see?

Footnotes should look the same in both places if possible.

[suzmue]

cc @matloob

[matloob]

This is interesting. footnotes don't seem to be mentioned in the github flavored markdown spec here: https://github.github.com/gfm/. Could you link us to official documentation of footnotes in github?

[madkins23]

• https://github.blog/changelog/2021-09-30-footnotes-now-supported-in-markdown-fields/
• https://docs.github.com/en/enterprise-cloud@latest/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#footnotes