function wfNoMarkupInTitle(ast, file, setting) {
  visit(ast, 'heading', function(node) {
    if (node.depth !== 1) {
      return;
    }
    node.children.forEach((child) => {
      if (validHeadingTypes.indexOf(child.type) === -1) {
        let msg = 'Top level headings must only contain text.';
        file.message(`${msg} Contained: ${child.type}`, node);
      }
    });
  });
}
Remark Lint Test - verifies there is no markup in level 1 headings.

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