fix(nuxt): ensure payload url has no protocol

[pi0]

🔗 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 like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Use URL parser to extract pathname from URL for internal _getPayloadURL utility and ensure input does not contain hostname or search params.

Previously an invalid URL like loadPayload('/\\example.com') could be passed.

Credits to @OhB00 for discovering this.

📝 Checklist

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

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