Update systemd unit file example

Issue #454

server/drawpile-srv.service

@@ -4,9 +4,18 @@ After=network.target
 Documentation=man:drawpile-srv
 
 [Service]
+# Note: set this to the correct path and add -d or -c to load the right configuration file
 ExecStart=/usr/bin/drawpile-srv
-Type=notify
-NotifyAccess=main
+
+# The AppImage is not built with systemd integration at the moment,
+# so type=simple should be used with it:
+Type=simple
+Restart=always
+
+# If you're using a self-built or distribution provided version with
+# systemd integration, use this to enable socket activation:
+#Type=notify
+#NotifyAccess=main
 
 # Note: in order to use session recording and SSL safely,
 # a dedicated user account should be created for drawpile-srv.