feat(rules): add vat rule

[julienbenac]

🔗 Linked issue

No linked issue or discussion.

❓ 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

This PR introduces a new vat validation rule for string schemas in VineJS, based on the validator library. No external library is added, so the core package size remains small.

// French VAT number validation
vine.string().vat({ countryCode: ['FR'] })

// German VAT number validation
vine.string().vat({ countryCode: ['DE'] })

// French or German VAT number validation
vine.string().vat({ countryCode: ['FR', 'DE'] })

📝 Checklist

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

[thetutlage]

Looks good. Can you open another PR for the docs?

[julienbenac]

Done vinejs/vinejs.dev#47 👍