Update navbar dropdown items

[scott-klaytn]

✨ Proposed Changes

• Enhanced navbar navigation flow by restructuring dropdown items to include key subcategories rather than popular pages. This change can improve user journey by providing clearer entry points to major content sections, allowing users to discover relevant information more intuitively through the sidebar navigation once they've selected their area of interest.
• Added dropdown items for Mini dApps category.

[AS-IS]

[TO-BE]

🗂️ Types of changes

• Minor Issues and Typos
• Major Content Contribution
• Others (e.g. platform-specific changes)

✅ Checklist

• I have read the CONTRIBUTING GUIDELINES.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

📌 Related issues

💡 Further comments