mpd: Use pipewire as the audio output

Now that pipewire is more mainstream, we don't have to worry about using
alsa or pulseaudio here which, from what I remember, took more effort
to set up.

mpd/.config/mpd/mpd.conf

@@ -8,4 +8,9 @@ pid_file           "~/.config/mpd/pid"
 state_file         "~/.config/mpd/state"
 sticker_file       "~/.config/mpd/sticker.sql"
 
+audio_output {
+  type "pipewire"
+  name "PipeWire Sound Server"
+}
+
 auto_update "yes"