Use cargo-deb to build a Debian package

This ships also a systemd service unit and a config file for
`/etc/default`

debian/default

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+ARGS=""
+
+# mightyohm-gc-exporter supports the following options:
+#  -a, --address <ADDRESS>            The IPv4 or IPv6 address where the metrics are served
+#                                     [default: 127.0.0.1]
+#  -b, --baud-rate <BAUD_RATE>        The baudrate of the serial connection [default: 9600]
+#  -p, --port <PORT>                  The port where the metrics are served [default: 9111]
+#  -s, --serial-port <SERIAL_PORT>    The port of the serial device, usually in '/dev/...'
+#                                     [default: /dev/serial0]
+#  -t, --timeout <TIMEOUT>            Timeout of the serial connection in ms [default: 1000]

debian/service

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+[Unit]
+Description=MightyOhm Geiger Counter exporter
+
+[Service]
+Group=dialout
+Restart=always
+EnvironmentFile=/etc/default/mightyohm-gc-exporter
+ExecStart=/usr/bin/mightyohm-gc-exporter $ARGS
+
+[Install]
+WantedBy=multi-user.target