on Non-FHS systems like NixOS, the system sounds are located
in /run/current-system/sw/share/sounds according to XDG specification
This patch allows the script to fallback to this directory if the
sound files are not found in /usr/share/sounds or $HOME/.local/share/sounds
Sounds script allows user to mute or use any compatible freedesktop sound theme for desktop sound effects.
This script will search in the home directory and system diretory for freedesktop sound themes to use.