docs(guide): add .client and .server components documentation

[huang-julien]

🔗 Linked issue

Hi 👋 I couldn't find any documentation about the .client components even if there was some *.client.vue components in the examples . This PR adds a small documentation for *.client.vue components, it also warn that directly importing a component (with direct path) does not work.

❓ 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

📝 Checklist

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

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[danielroe]

Thank you! ❤️

This looks good to me for now, but when #5689 is merged we will need to refactor this.

[pi0]

Thanks

[atinux]

Thank you ❤️