docs: add quick wins reference documentation

Add four high-impact quick reference guides:

- Integrations Overview: Comparison table of all built-in integrations
  (Prebid, Next.js, Permutive, Testlight) with features, endpoints,
  configuration examples, and use cases

- API Reference: Complete endpoint catalog with request/response formats,
  query parameters, authentication, examples for all first-party, signing,
  TSJS, and integration endpoints

- Environment Variables: Comprehensive guide to configuration via env vars
  including naming patterns, data type formats, secrets management, and
  complete examples for all integrations and settings

- Error Reference: Common errors, causes, and solutions organized by
  category (configuration, runtime, integrations, signing, build/deploy)
  with debugging tips and troubleshooting steps

Add new Reference section to sidebar with these guides for easy access

Author: ChristianPavilonis

docs/.vitepress/config.mts

@@ -27,7 +27,8 @@ export default defineConfig({
           { text: 'GDPR Compliance', link: '/guide/gdpr-compliance' },
           { text: 'Ad Serving', link: '/guide/ad-serving' },
           { text: 'First-Party Proxy', link: '/guide/first-party-proxy' },
-          { text: 'Creative Processing', link: '/guide/creative-processing' }
+          { text: 'Creative Processing', link: '/guide/creative-processing' },
+          { text: 'Integrations Overview', link: '/guide/integrations-overview' }
         ]
       },
       {
@@ -46,6 +47,14 @@ export default defineConfig({
           { text: 'Testing', link: '/guide/testing' },
           { text: 'Integration Guide', link: '/guide/integration-guide' }
         ]
+      },
+      {
+        text: 'Reference',
+        items: [
+          { text: 'API Reference', link: '/guide/api-reference' },
+          { text: 'Environment Variables', link: '/guide/environment-variables' },
+          { text: 'Error Reference', link: '/guide/error-reference' }
+        ]
       }
     ],