function setPlaybackSpeed(playbackSpeed) {
    /*
    Set the config playback speed.
    */
    _config2.default.playback_speed = playbackSpeed;

    /*
    Set the active song playback rate.
    */
    _config2.default.audio.playbackRate = _config2.default.playback_speed;
  }
Sets the playback speed for the song.

@param {number} playbackSpeed The speed we want the song to play back at.