Try to select the front cover as the poster for audio/music torrents

[Borewit]

Improve the poster selection for audio/music based torrent, aiming to get the cover-art selected as the torrent poster.

The poster selection function has an existing ToDo, indicating some more work needs to be done for audio based torrents:

webtorrent-desktop/src/renderer/lib/torrent-poster.js

Line 22 in 474654f

// TODO: generate a waveform from the largest sound file

Downloading the torrent from the audio album: Parov Stellar - The Princess currently results in the following:

[Borewit]

It does now select the correct poster in the index:

Playing the same track with this merge:

Putting the music-metadata merge (#1240) on top of that would give:

[codealchemist]

Closing after #1334.