add audio module

modules/audio.nix

@@ -0,0 +1,16 @@
+{ config, pkgs, lib, ... }:
+
+{
+  home.packages = with pkgs; [
+    ffmpeg
+  ];
+
+  programs.zsh.initContent = ''
+    function flac2aac() {
+      local dir="''${1:-.}"
+      for f in "$dir"/**/*.flac; do
+        [[ -f "$f" ]] && ffmpeg -i "$f" -c:a aac -b:a 256k -movflags +faststart "''${f%.flac}.m4a"
+      done
+    }
+  '';
+}