Enhance description of $(list-slice) function

Clarified description of the $(list-slice) function to include details about list indexing and omitting indices.

Signed-off-by: Hofi <hofione@gmail.com>

Author: HofiOne

doc/_admin-guide/110_Template_and_rewrite/000_Customize_message_format/007_Template_functions_of_syslog-ng.md

@@ -767,8 +767,9 @@ Available options:
 
 | *Syntax:* | $(list-slice \<from\>:\<to\> ${list} ) |
 
-*Description:* Returns the specified subset of the list. Note that the
-list index starts with zero, for example, $(list-slice 1:2 ${list} )
+*Description:* Returns the specified subset of the list. 
+
+The list index starts with zero, for example, $(list-slice 1:2 ${list} )
 returns the second and third element of the list, and so on.
 
 You can omit the from or to index if you want to start the subset from