feat(docs): Docusaurus multi-versioning, Developer Portal starter kit (#34271)

Co-authored-by: Claude <noreply@anthropic.com>

docs/versioned_docs/version-6.0.0/api.mdx

@@ -0,0 +1,35 @@
+---
+title: API
+hide_title: true
+sidebar_position: 10
+---
+
+import SwaggerUI from 'swagger-ui-react';
+import openapi from '/resources/openapi.json';
+import 'swagger-ui-react/swagger-ui.css';
+import { Alert } from 'antd';
+
+## API
+
+Superset's public **REST API** follows the
+[OpenAPI specification](https://swagger.io/specification/), and is
+documented here. The docs below are generated using
+[Swagger React UI](https://www.npmjs.com/package/swagger-ui-react).
+
+<Alert
+  type="info"
+  message={
+    <div>
+      <strong>NOTE! </strong>
+      You can find an interactive version of this documentation on your local Superset
+      instance at <strong>/swagger/v1</strong> (unless disabled)
+    </div>
+  }
+/>
+
+<br />
+<br />
+<hr />
+<div className="swagger-container">
+  <SwaggerUI spec={openapi} />
+</div>