feat: add an option to allow external packages to be scanned for Nuxt UI components

[ISOR3X]

🔗 Linked issue

Resolves #4892

❓ 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)
• ✨ 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

Allows adding external packages to be scanned for Nuxt UI components through the new allowedPackages option. This allows using Nuxt UI as a dependency for other projects.

📝 Checklist

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

[ISOR3X]

I wasn't sure about the name or location for the option. Besides the current option, I also considered extending ComponentsOptions since feature mostly relates to unplugin-vue-components. In the end I decided against it to keep that key purely for the options from that package.

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@5510

commit: fc02356

[benjamincanac]

I'm wondering if it wouldn't be easier to just remove this exclude, do you have a reproduction to try if it doesn't decrease performances?