Add small comment

apps/block_scout_web/lib/block_scout_web/chain.ex

@@ -535,6 +535,7 @@ defmodule BlockScoutWeb.Chain do
     %{"index" => index}
   end
 
+  # clause for zkEVM batches pagination
   defp paging_params(%TransactionBatch{number: number}) do
     %{"number" => number}
   end