Getstorybook CRNA support

[shilman]

why

Currently getstorybook requires a few extra steps to get working with create-react-native-app (aka CRNA). They are documented (excellently) here:

https://medium.com/@inyono/using-react-native-storybook-with-create-react-native-app-471e531bb128

what

Proposal for streamlining the setup process:

• Simplify as much as possible:
  • Consolidate storybook/index.ios.js and storybook/index.android.js into index.js
  • Detect CRNA app and print out additional (minimal) manual step
• Update docs: discuss why manual step and why manual step is necessary
  • react-native/README.md
  • react-native/docs
  • https://storybooks.js.org

Props to @orta and @tmeasday for helping figure this out and for @inyono for the awesome post.

[inyono]

That would be so awesome :) Btw: https://github.com/serlo-org/serlo-abc has an updated version of the blog post that e.g. picks the real app entry on build. Feel free to ask if you need input or want help from me.

[ndelangen]

Is this done?