init monlet repo with stage 0-2 (docs, contract, agent MVP)

agent/systemd/monlet-agent.service.example

@@ -0,0 +1,21 @@
+[Unit]
+Description=Monlet Agent
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=/usr/local/bin/monlet-agent -config /etc/monlet/agent.toml
+Restart=always
+RestartSec=5s
+User=monlet
+Group=monlet
+StateDirectory=monlet-agent
+NoNewPrivileges=true
+PrivateTmp=true
+ProtectSystem=strict
+ProtectHome=true
+ReadWritePaths=/var/lib/monlet-agent
+
+[Install]
+WantedBy=multi-user.target