Updates the top navigation items to match that of the project website (#4560)

Signed-off-by: Aaron Stephanus <taoist.futility@pm.me>

_data/top_nav.yml

@@ -1,4 +1,13 @@
 items:
+  -
+    label: OpenSearchCon
+    children:
+      -
+        label: Register for OpenSearchCon!
+        url: https://opensearchcon2023.splashthat.com
+      -
+        label: OpenSearchCon 2023 CFP!
+        url: /opensearchcon2023-cfp.html
   -
     label: Download
     fragments:
@@ -28,6 +37,7 @@ items:
       - community_projects
       - blog
       - partners
+      - slack
     children:
       -
         label: Blog
@@ -35,6 +45,9 @@ items:
       -
         label: Forum
         url: https://forum.opensearch.org/
+      -
+        label: Slack
+        url: /slack.html
       -
         label: Events
         url: /events
@@ -48,3 +61,16 @@ items:
     label: Documentation
     fragment: docs
     url: /docs/
+  -
+    label: Platform
+    children:
+      -
+        label: Vector Database
+        url: /platform/search/vector-database.html
+      -
+        label: Live Demo
+        url: https://playground.opensearch.org/
+      -
+        label: Performance Benchmarks
+        url: /benchmarks
+