Config arguments for documentation.formats.md

Running version 5.3.5, using this libs with Node.js API

The documentation on Node.js API says that `documentation.formats.md` accepts an optional second argument (args)

https://github.com/documentationjs/documentation/blob/7d74060caf3221dee8594845b8431dea4c2abf7a/docs/NODE_API.md#L127-L136

However, it isn't said what kind of options can be passed. It seems that the config options passed when using CLI affect both `build` and `formats` tasks. So I found out that using

```js
documentation.build('file.js',{
hljs: {
highlightAuto: true,
languages: ['js', 'json', 'sql', 'sh', 'bash']
}
}).then((res)=> {
return documentation.formats.md(res);
});
```
has no effect, (every example is highlighted as `javascript`) whereas

```js
documentation.build('file.js')
.then((res)=> {
return documentation.formats.md(res, {
hljs: {
highlightAuto: true,
languages: ['js', 'json', 'sql', 'sh', 'bash']
}
});
});
```

does indeed produce the right language highlighting.

Perhaps it should be added to documentation the usage of `hljs` and `paths` to `documentation.formats.md`.