🧭 Fix Left-Hand Navigation Bar in EvalAI Docs

**Description:**

The left-hand sidebar in the EvalAI documentation appears cluttered and unorganized. This affects usability and makes it harder for users to locate relevant sections quickly.

📸 **Screenshot for reference:**


### 🛠 Issues Identified:

* No clear grouping or hierarchy between related topics (e.g., challenge hosting vs participation vs development).
* Inconsistent naming conventions (e.g., some start with verbs, others are nouns).
* Redundant or scattered structure (e.g., "Submission" vs. "Make Submission Public/Private").
* Lack of collapsible sections for improved readability.

### ✅ Suggested Fix:

Refactor the sidebar navigation in the docs site with the following improvements:

* Group content under logical categories like:

* 🧪 Getting Started (Introduction, Installation)
* 🎯 Hosting a Challenge (Host Challenge, Challenge Configuration, Writing Evaluation Script, Approve Challenge)
* 🚀 Participating in Challenges (Participate, Make Submission Public/Private)
* ⚙️ Developer Guide (Pull Request, Contributing Guidelines, Directory Structure, Migrations, Architecture)
* 📚 Reference (Cite, FAQ, Glossary)

* Ensure consistent naming (e.g., use "Submit a Challenge", "Join a Challenge", etc.).

* Use collapsible/expandable headings (if the documentation theme supports it).

### 📍References:

* \[Current Docs Sidebar Screenshot attached above]

### 💡 Benefit:

Improving the navigation structure will significantly enhance documentation usability for new users, challenge hosts, and contributors.