add restart cmd, add example service file

Makefile

@@ -3,3 +3,7 @@
 build:
 	cargo build --release
 	ln -sf ./target/release/fedigroups .
+
+# if you have a service installed...
+restart:
+	sudo systemctl restart fedigroups

fedigroups.example.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=fedigroups daemon
+After=network.target
+
+[Service]
+User=bot
+SyslogIdentifier=fedigroups
+WorkingDirectory=/srv/bots/fedigroups/
+ExecStart=/srv/bots/fedigroups/fedigroups -v
+Restart=always
+RestartSec=15
+
+[Install]
+WantedBy=multi-user.target