export-default-from (Stage 1)

Champions: @jdalton @benjamn (prev @leebyron)
Spec Repo: https://github.com/tc39/proposal-export-default-from
Stayed at Stage 1 at the July 2017 meeting: https://github.com/tc39/agendas/blob/master/2017/07.md

Syntax

```js
export v from "mod";
```

## Implementation

Already implemented in https://babeljs.io/docs/plugins/transform-export-extensions/ but we should split it out

Start with the transform-export-extensions plugin documentation and the linked TC39 proposal to understand the existing export-default-from behavior. Identify how the current implementation is bundled and determine what must be separated; done means the proposal has its own implementation while preserving the documented syntax.

Written by the indexing model from the issue text.