title: Missing helpers and how to install them
body: <p>I noticed my epubs are not previewable by Recoll.</p>
  <p>My missing helpers are:</p>
  <pre><code>/opt/local/share/recoll/filters/rcldia (application/x-dia-diagram)
  /opt/local/share/recoll/filters/rclepub (application/epub+zip)
  /opt/local/share/recoll/filters/rclimg (image/png)
  /opt/local/share/recoll/filters/rclkar (audio/x-karaoke)
  /opt/local/share/recoll/filters/rclppt.py (application/vnd.ms-powerpoint)
  /opt/local/share/recoll/filters/rclzip (application/zip)
  info (application/x-gnuinfo)
  python3:chm (application/x-chm)
  python3:rarfile/python3:unrar (application/x-rar)
  </code></pre>
  <p>My question is how to install them?
  I installed epub: <code>pip install epub</code>.
  After restart of my Recoll, it did not make a different.
  Any help welcome, thanks!</p>