title: import 'package:flutter/foundation.dart'; no documentation for package
body: <p>I see this import statement in many examples but can't find any documentation for the package anywhere. </p>
  
  <pre><code>import 'package:flutter/foundation.dart';
  </code></pre>
  
  <p>Am I missing something obvious?</p>
  
  <p>Thanks.</p>