Updated SDRangel server with supervisor in Arch Linux (markdown)

SDRangel-server-with-supervisor-in-Arch-Linux.md

@@ -91,6 +91,8 @@ sudo systemctl stop supervisord
 sudo systemctl restart supervisord
 </pre>
 
+To have supervisord started at boot time:
+`sudo systemctl enable supervisord`
 
 # Web control