Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/idle.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": "idle",
+    "description": "Use the <code>chrome.idle</code> module to detect when the machine's idle state changes.",
+    "availability": "6",
     "types": [],
     "functions": [
       {
         "name": "queryState",
         "type": "function",
         "description": "Returns \"locked\" if the system is locked, \"idle\" if the user has not generated any input for a specified number of seconds, or \"active\" otherwise.",
         "parameters": [
           {
             "name": "detectionIntervalInSeconds",
             "type": "integer",
@@ skipping 36 matching lines @@
           {
             "name": "newState",
             "type": "string",
             "enum": ["active", "idle", "locked"]
           }
         ]
       }
     ]
   }
 ]