Follow up to r16471 documenting the array parameters system of the useatcmd.

git-svn-id: https://svn.code.sf.net/p/rathena/svn/trunk@16472 54d463be-8e91-2dee-dedb-b68131a5f0ec

doc/script_commands.txt

@@ -2129,6 +2129,15 @@ This command will unbind a NPC event label from an atcommand.
 
 This command will execute a custom atcommand on the attached RID from a script.
 
+This command, whether invoked by a script or command, will set paremeters to
+an array .@atcmd_parameters$[index] starting with an index of 0.
+
+Example:
+@test Testing Command
+
+The above would reflect the .@atcmd_parameters$[0] to equal "Testing" and
+.@atcmd_parameters$[1] to equal "Command".
+
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