Upgrade to Storybook v7

[thibaudcolas]

Currently in the "late alpha" phase according to https://storybook.js.org/blog/first-class-vite-support-in-storybook/.

[lb-]

We are using this package with Storybook 7 in Wagtail, not sure if this issue is fixed.

Ahh, I see that it's just that this package itself does not use Storybook 7 yet.