also download types during `neu create`

Fixes #79

After this patch is applied, it will create neutralino.d.ts next to neutralino.ts in resources/js.

In order to make this work with the default template, you make the following changes to resources/js/main.js

1) add

// @ts-check

2) add

import './neutralino.js'

3) add a // @ts-ignore to ignore the Object is possibly 'null'. error from document.getElementById('info').innerHTML = ... (or add a runtime check that the element is not null).

You also need to add neutralino.d.ts to .gitignore, like how neutralino.js is already ignored in the template.

Once this is done, you get IDE tab completion and hints for Neutralino.filesystem.readDirectory and NL_CWD etc. (in vscode) without needing to add any bulid steps.

[ ] It might be better to make this opt-in because of the gitignore thing. I'm not sure how you'd want this done though (neutralino.config.json seting or command line --flag?)

neutralinojs / neutralinojs-cli

also download types during `neu create` #219