docs(README): document extendable layer setup for Nuxt projects

[mkucmus]

🔗 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)
• ✨ 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

Added instructions for using Nuxt as an extendable layer with createResolver

[antfu]

I wonder if we could just always suggest using the resolve in the example, instead of duplicating the session twice, which can be confusing to read.

[mkucmus]

I wonder if we could just always suggest using the resolve in the example, instead of duplicating the session twice, which can be confusing to read.

good idea, it's added 🙌🏼