Add support iterator

[Vlad Sirenko]

example

const { on } = require('events');
const { request } = require('https');
const html = require('htm');

function h(type, props, ...children) {
  return { type, props, children };
}

request('https://nodejs.org/en', async (res) => {
  const iterator = on(res, "data");
  const domIterator = html.bind(h).iterator(iterator);
  for await (const element of emitter) {
    console.log(element);
  }
}).end();

request('https://nodejs.org/en', async (res) => {
  const iterator = on(res, "data");
  const domEmitter = html.bind(h).emitter(iterator);
  domEmitter.on('div', (element) => {
    console.log('emitter', element);
  });
  domEmitter.on('end', () => {
    console.log('end');
  });
}).end();

[Vlad Sirenko]

Motivation
sometimes the page is too big, but you need to get the elements that are at the beginning
an iterator or emitter would allow you to get the information you need without going through the entire page