Feature Request: Store Theme Songs in the "theme-music" folder

[ItsAllAboutTheCode]

In addition to Jellyfin web client playing theme songs with the file naming scheme of "theme.*" (theme.mp3, theme.flac, theme.wav, etc...), it also supports playing audio files from a theme-music no matter what the file name is as per the documentation https://jellyfin.org/docs/general/server/media/shows#other.

The Request here is to add a plugin configuration option that allows users to choose to download theme songs a theme-music folder instead of a theme.mp3 or theme.flac file.
That will allow more flexibility to users as it allows play multiple theme songs to be played in order when visiting a Series or Season folder.
This will also pair well with a PR to add support to play theme-media in random order: jellyfin/jellyfin-web#5714.

Ideally it would be nice if the user can choose where to download Theme songs via a configuration option such as

• Series Name (2024)/theme-music/*
• Series Name (2024)/Season XX/theme-music/*

Therefore a user can put additional audio files in addition to what the plugin downloads into a layout such as follows

Series Name (2024)/
  theme-music/
   1. Series-Theme.mp3
  Season 01/
   theme-music/
      1. Season1-OP1.mp3
      2. Season1-OP2.flac
  Season 02/
   theme-music/
      1. Season2-OP.wav