Elaborate comment in hook example

Signed-off-by: Herman van Rink <rink@initfour.nl>

vzdump-hook-script.pl

@@ -1,6 +1,9 @@
 #!/usr/bin/perl -w
 
-# example hook script for vzdump (--script option)
+# Example hook script for vzdump (--script option)
+# This can also be added as a line in /etc/vzdump.conf
+# e.g. 'script: /usr/local/bin/vzdump-hook-script.pl'
+
 
 use strict;