Detect breakage of autolinks

[dontcallmedom]

It is possible to change a definition autolink syntax while keeping the final link unchanged (e.g. by forcing the id attribute); this typically happens when changing the dfn-for associated with a definition.

Now that webref distinguishes links and autolinks, it may be possible to detect when a change would affect autolinking specifications (as happened in w3c/mediacapture-main#986 (comment))