fix(nuxt): improve default prerender behaviour

[danielroe]

🔗 Linked issue

resolves #14676

❓ 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 adds default values for new nitro features (unjs/nitro#1294 and unjs/nitro#1223) - supporting default 10 page concurrency of prerendering and failing a build if any paths don't prerender successfully. (Users can add any paths they intend to fail to nitro.prerender.ignore, or disable this behaviour if they want.)

📝 Checklist

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