Great idea! I've been thinking about creating a repo that could store tours for other repos. That way, the community could contribute them, without needing to check them into the target repo itself. Similar-ish to the definitelytyped ecosystem that TypeScript built up

But annotations are linked to lines. As soon as one line changes (e.g., its content is no longer in line N but line N+ M, the annotation is meaningless). So tours would be need constant updates (otherwise tours would work for fixed versions of the repo only).