Functions exported as default not picked up

First off, thanks for super useful cli. Have been needing this myself for so long I was about to make it, then bumped into this!

The issue I am having is that exporting a function as default does not appear in created `index.js`. However `async` functions and object exports work as expected:

```js
export default { someThing, someOtherThing } // WORKS => export { default as things }
export default async function someFunc() {} // WORKS => export { default as someFunc }
export default function someOtherFunc() {} // DOES NOT WORK => (no output)
```