docs(platform): publish versioned interactive API reference (Swagger UI)

Move the generated api.html into a leaf bundle under docs/platform/api/reference/
so the aggregator copies it into each versioned docs tree. A tiny index.md stub
routes it through a raw-passthrough layout (type: swagger) that serves the
self-contained Swagger UI verbatim at /docs/platform/<version>/api/reference/,
and registers an entry in the API sidebar. Also link it from the API Reference
landing page.

Requires the companion layouts/swagger/single.html in the website repo.

Signed-off-by: Tamal Saha <tamal@appscode.com>

Author: tamalsaha

docs/platform/api/_index.md

@@ -8,3 +8,11 @@ menu:
 menu_name: docsplatform_{{.version}}
 section_menu_id: api
 ---
+
+# API Reference
+
+Browse the KubeDB Platform REST API by topic using the sections in the sidebar.
+
+For a live, try-it-out view of every endpoint, open the
+[**Interactive API Reference**](../reference/) — a self-contained Swagger UI
+generated from the OpenAPI spec for this release.

api.html docs/platform/api/reference/api.htmlapi.html renamed to docs/platform/api/reference/api.html

@@ -0,0 +1,13 @@
+---
+title: Interactive API Reference
+type: swagger
+layout: single
+menu:
+  docsplatform_{{.version}}:
+    identifier: api-reference-interactive
+    name: Interactive API Reference
+    parent: api
+    weight: 5
+menu_name: docsplatform_{{.version}}
+section_menu_id: api
+---