Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/i18n.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": "i18n",
+    "description": "An <em>internationalized</em> extension or app can be easily <em>localized</em> &mdash; adapted to languages and regions that it didn't originally support.",
     "types": [],
     "functions": [
       {
         "name": "getAcceptLanguages",
         "type": "function",
         "description": "Gets the accept-languages of the browser. This is different from the locale used by the browser; to get the locale, use <code>window.navigator.language</code>.",
         "parameters": [
           {
             "type": "function",
             "name": "callback",
@@ skipping 23 matching lines @@
         ],
         "returns": {
           "type": "string",
           "description": "Message localized for current locale."
         }
       }
     ],
     "events": []
   }
 ]