audio/flac/video/jellyfin: restructuring entries for better navigation

wiki/airsonic-advanced.md

@@ -1,7 +1,8 @@
 # Airsonic-Advanced
 
 [Airsonic-Advanced](https://github.com/airsonic-advanced/airsonic-advanced) is
-a free and open-source personal media streamer.
+a free and open-source personal media streamer mainly used for
+[music and audiobooks](./audio.md).
 It is a more modern implementation of [Airsonic](./airsonic.md) which in turn
 is a fork of [Subsonic](./subsonic.md).
 

wiki/airsonic.md

@@ -1,7 +1,7 @@
 # Airsonic
 
 [Airsonic](https://github.com/airsonic/airsonic) is a free and open-source
-personal media streamer.
+personal media streamer mainly used for [music and audiobooks](./audio.md).
 It is a fork of [Subsonic](./subsonic.md).
 Airsonic is not maintained anymore and therefore deprecated.
 A more modern implementation of it is

wiki/subsonic.md

@@ -1,7 +1,7 @@
 # Subsonic
 
 [Subsonic](https://www.subsonic.org) is a personal media streamer mostly used
-for music.
+for [music and audiobooks](./audio.md).
 It is non-free and closed-source.
 There are free and open-source alternatives named [Airsonic](./airsonic.md) and
 [Airsonic-Advanced](./airsonic-advanced.md).