docs(contributing): Add contribution guide for v3

[HugoRCD]

🔗 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)
• ✨ 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

📝 Checklist

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

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@3076

commit: 094fdcf

[cloudflare-workers-and-pages]

Deploying ui3 with    Cloudflare Pages

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[benjamincanac]

Great initiative @HugoRCD! Just an idea but maybe we should name the file Contribution / /docs/content/1.getting-started/contribution.md to match https://nuxt.com/docs/community/contribution?

Also, I would mention tests next to Typecheck to let people know that we have to run test and test:vue and press u to update snapshots if needed.