function wfDGCLinks(ast, file, setting) {
  let msg = 'Do not hard code `developers.google.com` in links.';
  visit(ast, 'link', function(node) {
    let parsedUrl = url.parse(node.url);
    let hostname = parsedUrl.hostname;
    if (hostname && hostname.toLowerCase() === 'developers.google.com') {
      file.message(msg, node);
    }
  });
}
Remark Lint Test - verifies links are not hard coded to d.g.c.

@param {Object} ast
@param {Object} file
@param {Object} setting