Added exporter for Grandmaster, borderClocl and client clock

exporters/systemd/nexus-ptp-exporter.service

@@ -0,0 +1,22 @@
+[Unit]
+Description=Prometheus exporter for NYATER Nexus PTP
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=ptp-exporter
+Group=ptp-exporter
+EnvironmentFile=-/etc/default/nexus-ptp-exporter
+ExecStart=/opt/ptp-exporter/venv/bin/python /opt/ptp-exporter/nexus_ptp_exporter.py \
+    --host ${NEXUS_HOST} \
+    --target-name ${NEXUS_NAME} \
+    --username ${NEXUS_USER} \
+    --key-file ${NEXUS_KEY_FILE} \
+    --listen 0.0.0.0 \
+    --port 9560
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target