content(unstorage): fix documentation link

[cngJo]

🔗 Linked issue

I didn't create an issue for this small change to prevent spam - if it's important, I'm more than happy to create one after the fact :-)

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 📰 Content (a new article or a change in the content folder)
• 🐞 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)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The "Documentation" link on https://unjs.io/packages/unstorage pointed to the GitHub repository instead of https://unstorage.unjs.io/ like other packages do.

📝 Checklist

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