function renderMarkdown(content, {markdown, root}) {
  renderer._root = root;
  renderer._dirname = markdown.replace(/[^\/]*$/, '');
  renderer._path = markdown.slice(markdown.indexOf('docs/'));
  return marked(content, {renderer});
}
This map allows you to rewrite urls present in the markdown files
to be rewritted to point to other targets. It is useful so that
links can works both by browsing the docs using the Github explorer
and on the website.

If rewrite returns a falsy value, it will transform the link to a simple
text, in case you don't want this link to point to anything.