feat(nuxi): auto-generate .npmrc and setting for pnpm

[kecrily]

🔗 Linked issue

ref nuxt/nuxt#14146

❓ 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Before we support using pnpm without --shamefully-hoist, let's automatically generate .npmrc for an out-of-the-box experience. Remove it after support.

📝 Checklist

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

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[pi0]

I really love the idea of this PR! But I think which-pm-runs only works when running nuxi init with pnpm and in docs we also use npx which could be misleading if someone uses npx + pnpm install.

[kecrily]

This is really a problem. Maybe we can clarify this in the documentation?