Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/windows.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": "windows",
+    "description": "Use the <code>chrome.windows</code> module to interact with browser windows. You can use this module to create, modify, and rearrange windows in the browser.",
     "compiler_options": {
       "implemented_in": "chrome/browser/extensions/api/tabs/tabs_api.h"
     },
     "dependencies": [ "tabs" ],
     "types": [
       {
         "id": "Window",
         "type": "object",
         "properties": {
           "id": {"type": "integer", "optional": true, "minimum": 0, "description": "The ID of the window. Window IDs are unique within a browser session. Under some circumstances a Window may not be assigned an ID, for example when querying closed windows from the $ref:sessionRestore API."},
@@ skipping 250 matching lines @@
         "name": "onFocusChanged",
         "type": "function",
         "description": "Fired when the currently focused window changes. Will be chrome.windows.WINDOW_ID_NONE if all chrome windows have lost focus. Note: On some Linux window managers, WINDOW_ID_NONE will always be sent immediately preceding a switch from one chrome window to another.",
         "parameters": [
           {"type": "integer", "name": "windowId", "minimum": -1, "description": "ID of the newly focused window."}
         ]
       }
     ]
   }
 ]