🚀 Feature: Lint for missing relative links in Markdown files

[JoshuaKGoldberg]

Bug Report Checklist

• [X] I have tried restarting my IDE and the issue persists.
• [X] I have pulled the latest main branch of the repository.
• [X] I have searched for related issues and found none that matched my issue.

Overview

I just discovered the hard way that the README.md contains an incorrect path for a relative link 😱:

https://github.com/JoshuaKGoldberg/create-typescript-app/blob/30ea110a303193c783f50aa232e06bdca25ec04e/README.md#L48

(the file name is Migration.md, not Migrate.md)

That kind of typo should have been caught in CI. Surely there's some lint rule somewhere that could do this?

Additional Info

I did a quick Google and found https://github.com/theoludwig/markdownlint-rule-relative-links. Maybe that's usable?

If we end up switching to eslint-plugin-mdx or some such (#567), we'd want a lint rule from that config/plugin.

[Paulie-Aditya]

why don't we just change the docs to say ./docs/Migration.md ?

[JoshuaKGoldberg]

Not sure what you mean there. This issue is for adding tooling that will automatically find incorrect links, not about any specific incorrect link that exists today.