local-looper: Add a simplified looper system that is not dependent on network connectivity.

cmd/local-looper/README.md

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+# DESCRIPTION
+	local looper is a process which will continually loop a pcm audio file
+	(like looper). The intended hardware for this system is a raspberry pi
+	zero W, with a USB sound card (AUDIODEV=hw:(1,0)).
+
+# AUTHORS
+	David Sutton <davidsutton@ausocean.org>
+
+# SETUP
+	1) move looper.sh to home/pi and run "chmod u+x looper.sh.
+	2) move looper.service to /etc/systemd/system.
+	3) run systemctl enable looper.service.
+	4) run sudo systemctl start looper.service.
+	5) restart the device, and wait for boot and audio should play.

cmd/local-looper/looper.service

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+[Unit]
+Description=Loop PCM audio file on boot
+After=network.target
+
+[Service]
+User=pi	
+WorkingDirectory=/home/pi/
+ExecStart=/bin/bash /home/pi/looper.sh
+
+[Install]
+WantedBy=multi-user.target

cmd/local-looper/looper.sh

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+#!/bin/bash
+
+export AUDIODEV=hw:1,0
+while true; do
+  play -q -V0 -t raw -r 44.1k -e signed -b 16 -c 1 /home/pi/shrimp.pcm
+done