fix: ensure deterministic icon sort order in client bundle

[andreasgangso]

Sort icons alphabetically within each collection to ensure idempotent output regardless of discovery order

🔗 Linked issue

Resolves #445

❓ 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

I'd like to cache the client bundle but currently it easily changes between runs when using a config like:

clientBundle: {
    includeCustomCollections: true,
    scan: true,
}

It's because the order of the keys in each collection's "icons" object is not consistent.