src/language-markdown/printer-markdown.js/shouldPrePrintDoubleHardline
function shouldPrePrintDoubleHardline(node, data) {
  const isSequence = (data.prevNode && data.prevNode.type) === node.type;
  const isSiblingNode =
    isSequence && SIBLING_NODE_TYPES.indexOf(node.type) !== -1;

  const isInTightListItem =
    data.parentNode.type === "listItem" && !data.parentNode.loose;

  const isPrevNodeLooseListItem =
    data.prevNode && data.prevNode.type === "listItem" && data.prevNode.loose;

  const isPrevNodePrettierIgnore = isPrettierIgnore(data.prevNode);

  return (
    isPrevNodeLooseListItem ||
    !(isSiblingNode || isInTightListItem || isPrevNodePrettierIgnore)
  );
}