Document the --linefeed option in README

Author: ngarratt

README.md

@@ -48,6 +48,7 @@ Copy `check_netapp_ontap.pl` script to your nagios libexec folder and configure
 * --warning, -w => A custom warning threshold value. See the option and threshold list at the bottom of this help text.
 * --critical, -c => A custom warning threshold value. See the option and threshold list at the bottom of this help text.
 * --modifier, -m => This modifier is used to set an inclusive or exclusive filter on what you want to monitor.
+* --linefeed, -l => Add linefeeds between multi-line diagnostic output entries.
 * --help, -h => Display this help text.
 
 ### Options