fix(vinejs): add exists and unique bindings to VineNumber

[Tahul]

🔗 Linked issue

#997

❓ Type of change

• 🐞 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

Resolves #997 by injecting exists and unique in VineNumber as well.

It also adds it to the type augmentation declaration.

📝 Checklist

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

[thetutlage]

Thanks 👍