fix(test-utils): import jest.fn from @jest/globals

[danielroe]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This uses @jest/globals to import jest.fn from: https://jestjs.io/docs/api.

We might consider not adding as a dep given how heavy it is. wdyt @antfu?

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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[antfu]

Looks ok. Do we need to explicitly external it?

[danielroe]

I've added to (optional) peerDeps - but again, happy if you have a different suggestion!