add mjolnir systemd unit

systemd/system/mjolnir.service

@@ -0,0 +1,41 @@
+[Unit]
+Description=mjolnir bot
+After=synapse.service
+
+[Service]
+CapabilityBoundingSet=
+ExecStart=/usr/bin/node /opt/mjolnir/lib/index.js
+IPAddressDeny=any
+IPAddressAllow=localhost
+LockPersonality=true
+NoNewPrivileges=true
+PrivateDevices=true
+PrivateIPC=true
+PrivateTmp=true
+PrivateUsers=true
+ProcSubset=pid
+ProtectClock=true
+ProtectControlGroups=true
+ProtectHome=true
+ProtectHostname=true
+ProtectKernelLogs=true
+ProtectKernelModules=true
+ProtectKernelTunables=true
+ProtectProc=invisible
+ProtectSystem=strict
+ReadWritePaths=/var/lib/mjolnir
+Restart=on-failure
+RestartSec=5s
+RestrictAddressFamilies=AF_INET AF_INET6
+RestrictNamespaces=true
+RestrictRealtime=true
+RestrictSUIDSGID=true
+SystemCallArchitectures=native
+SystemCallFilter=@system-service pkey_mprotect pkey_alloc pkey_free
+SystemCallFilter=~@privileged @resources @obsolete
+UMask=0077
+User=mjolnir
+WorkingDirectory=/var/lib/mjolnir
+
+[Install]
+WantedBy=multi-user.target