fix: create dummy package.json for ESM compatibility

[tobiasdiez]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

If you have type: module in your main package.json, then storybook doesn't work. This is not an issue with the nuxt module, but with upstream storybook, see storybookjs/storybook#11587.
In this issue, a workaround is outlined which involves creating a package.json in the storybook folder.
This is added with this PR.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes (if not applicable, please state why)