Add command line parameter for resolver

[fkling]

--resolver findAllComponentDefinitions would use https://github.com/reactjs/react-docgen/blob/master/src/resolver/findAllComponentDefinitions.js.

--resolver ./path/to/resolver.js would use a custom resolver.

This allows to use another resolver without having to write a custom script.

[ondrejbartas]

nice 👍

[vieron]

+1