feat: update documentation source and add index.md

- Changed documentation source from 'documentation.md' to 'index.md' in content.config.ts.
- Added new index.md file containing comprehensive documentation for ArtMCP, including installation, tools, prompts, resources, MCP integration, and API endpoints.
- Updated GitHub repository configuration in nuxt.config.ts for consistency.
- Bumped dependencies in package.json to latest versions for improved functionality and security.

content.config.ts

@@ -106,7 +106,7 @@ export default defineContentConfig({
     }),
     documentation: defineCollection({
       type: 'page',
-      source: 'documentation.md'
+      source: 'index.md'
     })
   }
 })