Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/declarative_web_request.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": "declarativeWebRequest",
+    "description": "Use the <code>chrome.declarativeWebRequest</code> module to intercept, block, or modify requests in-flight. It is significantly faster than the <a href='webRequest.html'><code>chrome.webRequest</code> API</a> because you can register rules that are evaluated in the browser rather than the JavaScript engine with reduces roundtrip latencies and allows higher efficiency.",
     "documentation_permissions_required": ["declarative", "declarativeWebRequest"],
     "types": [
       {
         "id": "HeaderFilter",
         "type": "object",
         "description": "Filters request headers for various criteria. Multiple criteria are evaluated as a conjunction.",
         "properties": {
           "namePrefix": {
             "description" : "Matches if the header name starts with the specified string.",
             "type": "string",
@@ skipping 564 matching lines @@
               "tabId": {"type": "integer", "description": "The ID of the tab in which the request takes place. Set to -1 if the request isn't related to a tab."},
               "type": {"type": "string", "enum": ["main_frame", "sub_frame", "stylesheet", "script", "image", "object", "xmlhttprequest", "other"], "description": "How the requested resource will be used."},
               "timeStamp": {"type": "number", "description": "The time when this signal is triggered, in milliseconds since the epoch."}
             }
           }
         ]
       }
     ]
   }
 ]