qemush : mise à jour du message d'aide

bin/qemush

@@ -46,7 +46,7 @@ ${name}: usage:
   ${name} diskrm <disk name>               - delete disk image
   ${name} shell                            - start a shell as user qemu
   ${name} help                             - show this help
-  ${name} add <path to script>        - add a launching script from this PATH
+  ${name} add <path to script> [<VM name>] - add a launching script
 EOF
 }