Add documentation subsections to top menu

Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>

_data/top_nav.yml

@@ -85,8 +85,26 @@ items:
         url: /community_projects
   -
     label: Documentation
-    fragment: docs
-    url: /docs/
+    fragments: 
+      - docs
+      - opensearch
+      - data-prepper
+      - clients
+      - benchmark
+    url: /docs/latest/
+    children:
+      -
+        label: OpenSearch and Dashboards
+        url: /docs/latest/about/
+      -
+        label: Data Prepper
+        url: /docs/latest/data-prepper/
+      -
+        label: Clients
+        url: /docs/latest/clients/
+      -
+        label: Benchmark
+        url: /docs/latest/benchmark/
   -
     label: Platform
     url: /platform/index.html