added systemd service file

sauerbraten.service

@@ -0,0 +1,26 @@
+[Unit]
+Description=Sauerbraten Server container based on https://github.com/andrius4669/zeromod-sauerbraten
+
+[Service]
+Slice=machine.slice
+# Resource limits
+Delegate=true
+CPUShares=256
+MemoryLimit=128M
+
+Environment=ROOT_DIR=/srv/sauerbraten
+Environment=SAUER_PORT=4700
+Environment=SAUER_CMD="-d1 -c18 -g2"
+
+ExecStartPre=/bin/mkdir -p ${ROOT_DIR}
+ExecStart=/usr/bin/rkt --insecure-options=image run --dns 8.8.8.8 --inherit-env --volume volume-opt-sauerbraten,kind=host,source=${ROOT_DIR} \
+                       --port 28785-udp:${SAUER_PORT}5 --port 28786-udp:${SAUER_PORT}6 --port 28785-tcp:${SAUER_PORT}5 --port 28786-tcp:${SAUER_PORT}6 \
+                       docker://repo.shimun.net/sauerbraten -- ${SAUER_CMD} --- --memory=64M
+
+ExecStopPost=/usr/bin/rkt gc
+KillMode=mixed
+Restart=always
+RestartSec=30
+
+[Install]
+WantedBy=multi-user.target