src/language-markdown/printer-markdown.js/isPrettierIgnore
function isPrettierIgnore(node) {
  let match;

  if (node.type === "html") {
    match = node.value.match(/^<!--\s*prettier-ignore(?:-(start|end))?\s*-->$/);
  } else {
    let comment;

    if (node.type === "esComment") {
      comment = node;
    } else if (
      node.type === "paragraph" &&
      node.children.length === 1 &&
      node.children[0].type === "esComment"
    ) {
      comment = node.children[0];
    }

    if (comment) {
      match = comment.value.match(/^prettier-ignore(?:-(start|end))?$/);
    }
  }

  return match ? match[1] || "next" : false;
}