Alias system

I was thinking about something like that:

```js
{
  javascript: {
    engines: { /* ... */ }
  },
  js: {
    alias: "javascript"
  }
}
```

or : 

```js
{
  javascript: {
    alias: "js",
    format: "children",
    children: {
      engines: { /* ... */ }
    }
  }
}
```

But have several way in a framework to do something is not a good thing. (I think) 🤔 