src/language-markdown/utils.js/getFencedCodeBlockValue
function getFencedCodeBlockValue(node, originalText) {
  const { value } = node;
  if (
    node.position.end.offset === originalText.length &&
    value.endsWith("\n") &&
    // Code block has no end mark
    originalText.endsWith("\n")
  ) {
    return value.slice(0, -1);
  }
  return value;
}