[FEATURE REQUEST] Allow choosing custom decoder/player

[MSOB7YY]

some users are struggling with playing some formats (like flac/alac)
either crashes (alac) or stops after 20/30 seconds (flac)

apparently this seems like an issue only with exoplayer with a default decoder

solutions:

• internally modify how decoders are chosen (no experience in this)
• simply allow changing the player/decoder
  1. Default (HW decoder): good with most formats, can fallback to ffmpeg extension if it cant play smth, but sometimes won't (which is why the issues happen)
  2. ffmpeg (SW decoder): can play almost all formats like mpv, only issue is high cpu/battery usage due to it being a software decoder
  3. mpv: currently it's only used for windows. it can be used for android but will miss some features (ex. looping animations)

list of issues related/can be closed by implementing this:
#346 #555 #687 #698 #732 #715

[MSOB7YY]

an update, i'm not going to proceed with this. recent changes here MSOB7YY/just_audio@ab240a4 & here MSOB7YY/just_audio@32ede74 added more support for these files by default, without needing to enable sw decoder or changing player.

also mpv for android introduces about 7mb to the apk size (not much but is when it's just an option), and that is while missing features that were implemented for default player,

• like:
  • skip silence
  • looping animations
  • gapless
  • equalizer
  • equalizer presets
  • loudness enhancer
  • quick settings tile
  • picture in picture

TLDR: download the latest beta (v5.4.6+) https://github.com/namidaco/namida-snapshots/releases and you are good to go