Add systemd service and Makefile for Linux installation

grokway.service

@@ -0,0 +1,31 @@
+[Unit]
+Description=Grokway Server Service
+After=network.target
+
+[Service]
+# User/Group to run as.
+User=grokway
+Group=grokway
+
+# Working Directory. This is important because the code relies on relative paths
+# like ./cmd/server/static.  If we install everything to /opt/grokway, this works.
+WorkingDirectory=/opt/grokway
+
+# Path to the executable.
+ExecStart=/opt/grokway/grokway
+
+# Environment variables.
+# You MUST set this to a secure token, otherwise a random one is generated on each start.
+#Environment=GROKWAY_TOKEN=your-very-secure-token
+
+# Restart policy.
+Restart=always
+RestartSec=5
+
+# Standard output/error logging.
+StandardOutput=syslog
+StandardError=syslog
+SyslogIdentifier=grokway
+
+[Install]
+WantedBy=multi-user.target