title: Injected scripts in Opera extensions
body: <p>I'm trying to "port" my Chrome-extension to Opera. My extension does nothing else but edits the DOM a little bit. In Chrome extension I use contentscript and based on my research the similar way for Opera is injected scripts. Anyway, <a href="http://www.opera.com/docs/apis/extensions/injectedscriptsguide/" rel="nofollow">the documentation</a> doesn't really tell how should I use injected scripts.</p>
  
  <p>I have the js-file in <code>includes/</code> but seems like it doesn't include automatically. I also need to specify domains to inject the script on.</p>
  
  <p>Currently my file has this content for testing purposes:</p>
  
  <pre><code>window.addEventListener('load', function() {
      alert('asd');
  });
  </code></pre>
  
  <p>Any help is appreciated :)</p>