Add support iterator

example

```js
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();
```

Start with the issue's Node.js example and compare the requested html.bind(h).iterator(iterator) API with the shown .emitter(iterator) usage. Trace the existing htm binding entry point and determine the expected behavior for the async iterator and its completion; the work is done when the documented example runs with the intended element output.

索引モデルが issue の本文から書いたものです。