Support multiple exports

Hi there,

I was just wondering if you'd consider supporting files that export multiple components?

I noticed in here that you just take the first component: https://github.com/atlassian/extract-react-types/blob/master/packages/extract-react-types/src/index.js#L132

I'm happy to submit a PR for this, just wanted to see if that would be something you'd be open to supporting?

Thanks