Auto-numbering episodes

[timosturm]

Clear and concise description of the problem

Some podcasts do not provide the track in the mp3 files (ID3 tag).

Suggested solution

It would be nice if this could (optionally) be set from the track position in the RSS-feed instead. Either by setting the tag, or by adding it as a prefix to the file-name: 001 - <episode-title>.

Additional context

This makes it easier to handle / organize the podcast outside of podfetch.

Example of such a podcast: https://verbrechen.podigee.io/feed/mp3 or this: http://revolutionspodcast.libsyn.com/rss/, which is really a shame as the order of episodes really does matter here.

I added a detailed description in this comment.

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