From my initial thoughts it seems to make sense to start with storybook in the same repository for now. That should represent the state of the components at the tip of the master branch and facilitate communication from developers to UX.

In the future I see a need for something similar to the OOUI demo page.
This could then be maintained in a separate repository which would have several benefits:

• easier to edit by UX people
• changing only the documentation doesn't touch the component repository + doesn't trigger component CI
• easier to maintain versioned documentation (if desired)