[@next/storybook] _app.js must be imported within stories for global css to apply

Bug report

Describe the bug

When using the @next/storybook preset, use of global css is possible, but it must be added to _app.js within the pages folder, and then the story utilizing the global css must import _app.js. While this works, it’s an unusual and unintuitive, so I would assume the aim would be to eliminate this pattern.

To Reproduce

1. Check out this reproduction repo
2. Note that in order for global css to apply, the _app file must be imported within the story. If it is not imported, css does not apply.

Expected behavior

This is a tough one, I don’t feel like the preset should actually require pages as a folder to be present at all. I’d say the ideal solution for this might be adding some sort of globalCss option to the preset where global css files could be specified - this would remove the dependence on pages, _app.jsx and the _app.jsx import.

System information

• OS: macOS
• Version of Next.js: 9.4.4
• Version of Node.js: 12.13.0

[Vadorequest]

I didn’t encounter much difficulties regarding global styles, because next v10 allows to have them in a separate file as _app, so it was rather easy to import them in .storybook/preview.js

See PR: https://github.com/UnlyEd/next-right-now/pull/251

[itsajay1029]

Can you assign this to me @nfroidure ?