ESM support

[Homa Wong]

Is there any plan to update and support ESM?

There was a closed issue in the past #235, but that's old and is about adding module: '...'.

It would be great to support proper ESM:

{
  "type": "module",
  "exports": {
    "import": "./esm/index.js",
     "require": "./cjs/index.js" // if supporting both ESM and cjs
   }
}