Add --music-output-device to route music separately from voice (#350)

* Add --music-output-device to route music separately from voice

Music/media and TTS both play through --audio-output-device today, with no
way to send them to different sinks. Add an optional --music-output-device
(env MUSIC_OUTPUT_DEVICE) that the music player uses instead, defaulting to
--audio-output-device so existing setups are unchanged. Wired through
docker-entrypoint.sh and documented in the README and install docs.

* docs: fix swapped Default/Description columns in env var table

The MIC_VOLUME, MIC_AUTO_GAIN, MIC_NOISE_SUPPRESSION and
AUDIO_INPUT_CHANNELS rows had their Default and Description columns
swapped relative to the table header; fix the ordering and the
'Suppresion' misspelling. Also repair the UNMUTE_SOUND row, whose
description was garbled and which was missing its closing table pipe.

---------

Co-authored-by: Matthew Davis <fedoraproject@virtual.drop.net>
Co-authored-by: Florian Asche <github@florian-asche.de>
Co-authored-by: Omar Amin <65174210+omaramin-2000@users.noreply.github.com>

docker-entrypoint.sh

@@ -44,6 +44,10 @@ if [ -n "${AUDIO_OUTPUT_DEVICE}" ]; then
   EXTRA_ARGS+=( "--audio-output-device" "$AUDIO_OUTPUT_DEVICE" )
 fi
 
+if [ -n "${MUSIC_OUTPUT_DEVICE}" ]; then
+  EXTRA_ARGS+=( "--music-output-device" "$MUSIC_OUTPUT_DEVICE" )
+fi
+
 if [ -n "${MIC_VOLUME}" ]; then
   EXTRA_ARGS+=( "--mic-volume" "$MIC_VOLUME" )
 fi