rived from the resources, and tools can 
rebuild it at any time (or built it and add it if it is not present).
</p>
<pre class="json">
{
  "index-version": 2,
  "files": [
  ]
}
</pre>
<p>
The index version is a fixed value that may change if this file format
is changed. Tools should rebuild the file if they do not recognize
the version. The files array contains an object for each resource 
in the package with the following properties:
</p>
<ul>
  <li>filename - the filename in the package 