Fix sidebar categories to eliminate duplicate entries

[bhouston]

Improve Sidebar Navigation and Eliminate Duplicate Entries

This PR addresses issue #34 by adding _category_.json files with a specialized configuration that eliminates duplicate entries in the sidebar navigation.

Problem Solved

Previously, we had duplicate entries in the navigation:

• Both a standalone "Getting Started" page and a "getting-started" category
• Both a standalone "Usage" page and a "usage" category

Solution Implemented

• Added _category_.json files to customize category display names
• Configured categories to use the main pages as their index pages instead of auto-generated indexes
• This makes the main pages serve as both category entries and content pages

Changes Made

1. Added _category_.json to the getting-started directory:

   {
     "label": "Getting Started",
     "position": 2,
     "link": {
       "type": "doc",
       "id": "getting-started"
     }
   }

2. Added _category_.json to the usage directory:

   {
     "label": "Usage Guide",
     "position": 3,
     "link": {
       "type": "doc",
       "id": "usage"
     }
   }

Before / After

Before:

• Duplicate entries in sidebar
• Categories displayed as lowercase, hyphenated directory names

After:

• Clean navigation with proper category labels
• No duplicate entries
• Main pages serve as both category entries and content pages

This approach maintains the existing directory structure and content organization while providing a more professional and user-friendly navigation experience.