Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/omnibox.json

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
   {
     "namespace": "omnibox",
+    "description": "The omnibox API allows you to register a keyword with Google Chrome's address bar, which is also known as the omnibox.",
     "types": [
       {
         "id": "SuggestResult",
         "type": "object",
         "description": "A suggest result.",
         "properties": {
           "content": {
             "type": "string",
             "minLength": 1,
             "description": "The text that is put into the URL bar, and that is sent to the extension when the user chooses this entry."
@@ skipping 91 matching lines @@
       },
       {
         "name": "onInputCancelled",
         "type": "function",
         "description": "User has ended the keyword input session without accepting the input.",
         "parameters": []
       }
     ]
   }
 ]