Add TypeScript, ESM, directly SVG string output interface support.

[PrinOrange]

Hi, there

I want to integrate this library into node.js project. I think for modern JavaScript development, the TypeScript and ESM support will benefit a lot.

And, I think it would be better if add a toSVG() method that output SVG string directly. Like:

let smilesDrawer = new SmilesDrawer.Drawer(options);
smilesDrawer.toSVG(" ... SMILES CODE... ") // => <svg> ... </svg>

[xavierholt]

Typescript is a good idea, but that's a pretty big change. I'll try to work it in as I refactor things, but I'm just an assistant maintainer, and this is a complicated project, so change will come slowly.

In the meantime, if you need an SVG as a text string, you can use this:

SmilesDrawer.parse(smiles, function(molecule) {
  let drawer = new SmilesDrawer.SvgDrawer({})
  let svg  = drawer.draw(molecule, 'svg')
  let text = svg.outerHTML
  // ...
}, function(error) {
  console.log(error)
})