Default values for props are not always extracted #155

The default value for props does not always seem to get extracted by extract-react-types.

One place where this is very visible is https://atlassian.design/components/button/code which has no default value information (despite having default values for many of the props).

As @danieldelcore indicated on Slack this is likely because:

I suspect it only pulls defaults off a component from the Component.defaultProps property or via static defaultProps rather than destructured function args

It would be great if extract-react-types could support extracting default values for props that are defined through default values on destructured function args 😄