src/language-markdown/mdx.js/esSyntax
function esSyntax() {
  const { Parser } = this;
  const tokenizers = Parser.prototype.blockTokenizers;
  const methods = Parser.prototype.blockMethods;

  tokenizers.esSyntax = tokenizeEsSyntax;

  methods.splice(methods.indexOf("paragraph"), 0, "esSyntax");
}