src/language-markdown/pragma.js/startWithPragma
function startWithPragma(text) {
  const pragma = `@(${pragmas.join("|")})`;
  const regex = new RegExp(
    [
      `<!--\\s*${pragma}\\s*-->`,
      `<!--.*\r?\n[\\s\\S]*(^|\n)[^\\S\n]*${pragma}[^\\S\n]*($|\n)[\\s\\S]*\n.*-->`,
    ].join("|"),
    "m"
  );
  const matched = text.match(regex);
  return matched && matched.index === 0;
}