parseChartEpisode function
Parses an episode from the charts data.
Implementation
JsonMap parseChartEpisode(JsonMap data) {
  final episode = parseEpisode(data);
  episode.remove('index');
  episode['podcast'] = parseIdName(
    nav(data, ['secondTitle', 'runs', 0]) as JsonMap?,
  );
  episode['duration'] = nav(data, SUBTITLE2, nullIfAbsent: true);
  return episode;
}