Resolve "Validation locale"

Closes #192 (closed)

lib/block/validation/local/transaction/transaction_count.ex

 defmodule Block.Validation.Local.TransactionCount do
+  @moduledoc """
+  Signatures count must be the same as issuers count
+
+  https://git.duniter.org/documents/rfcs/-/blob/master/rfc/0010_Duniter_Blockchain_Protocol_V12.md#transactions
+  """
   def valid(block) do
     Enum.all?(block["transactions"], fn element ->
       length(element["signatures"]) == length(element["issuers"])