Ah, I see what you mean. docs.github.com looks like it’s organized under a central repo so this is a bit easier to pull off. Our docs are spread out across many repos (mostly to make it easier for teams to update) and not everything is in GitHub.
For notebooks, we lint check 1 if there are buttons in the source files. And could potentially require this in plain Markdown files (though notebooks are the dominant documentation format on the website).