Fix broken link

[Y-Nak]

Fix some broken internal links.

[jackh726]

Thanks!

It's surprising to me that mdbook-linkcheck didn't pick these up. @Michael-F-Bryan

[Michael-F-Bryan]

I had a look into this and don't believe mdbook-linkcheck is missing broken links here, it seems to be how browsers handle the file:// protocol and absolute links.

When you open a document from the filesystem (i.e. mdbook build --open) and click on a link to /clauses.html the browser will dutifully navigate to file:///clauses.html instead of the intended file:///home/michael/Documents/forks/chalk/book/book/clauses.html (or wherever the page happens to be). When served from a web server (i.e. mdbook serve or https://rust-lang.github.io/chalk/book/) this is all handled correctly.

Would it be worth adding some sort of "warn-on-absolute-links" check to mdbook-linkcheck to help people avoid this issue in the future?

[jackh726]

A warning might be nice :)