collapsed links and reference links have a pretty particular syntax,
it seems unlikely they would show up on accident.
Co-authored-by: León Orell Valerian Liehr <me@fmease.dev>
This commit takes advantage of a feature in pulldown-cmark that
makes the list of link definitions available to the consuming
application. It produces unresolved link warnings for refdefs
that aren't used, and can now produce exact spans for the dest
even when it has escapes.
