check if the paragraph start with how many %

title_markdown_check.js

function processParagraph(paragraph) {
  var header = 0;
  while (paragraph.charAt(header) == "%")
    header++;
  if (header > 0)
    return {type: "h" + header, content: paragraph.slice(header + 1)};
  else
    return {type: "p", content: paragraph};
}