groups are also supported in menu (#982)

Author: dks333

navigation.mdx

@@ -152,10 +152,16 @@ Tabs can have menus that display dropdown navigation items that let users go dir
         {
           "item": "API References",
           "icon": "rocket",
-          "pages": [
-            "api-reference/get",
-            "api-reference/post",
-            "api-reference/delete"
+          "groups": [
+            {
+              "group": "API Reference",
+              "icon": "square-terminal",
+              "pages": [
+                "api-reference/get",
+                "api-reference/post",
+                "api-reference/delete"
+              ]
+            }
           ]
         },
         {