docs(header): add tip for title link's aria-label

[ra-jeev]

🔗 Linked issue

NA

❓ 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

Using the title slot of the header component doesn't change the aria-label of the link from its default value of Nuxt UI.

Add an explicit tip to still add the title prop along with the title slot for changing the aria-label.

📝 Checklist

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

[benjamincanac]

Thanks 😊

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@5340

commit: b027f3b