feat: add `@planship/nuxt` module

[pwojnaro]

🔗 Linked issue

Resolves https://github.com/nuxt/modules/issues/1062

❓ 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)
• [X] ✨ 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

This is the official Nuxt module for Planship that lets Nuxt developers add entitlements, metering, plan packaging, and subscription management to their apps.