Added all SEPA countries (IBANs from European Union countries) and minimal test coverage for countries

lib/iban_ex/country/mt.ex

@@ -1,6 +1,13 @@
 defmodule IbanEx.Country.MT do
   @moduledoc """
   Malta IBAN parsing rules
+
+  ## Examples
+
+    iex> %IbanEx.Iban{country_code: "MT", check_digits: "84", bank_code: "MALT", branch_code: "01100", national_check: nil, account_number: "0012345MTLCAST001S"}
+    iex> |> IbanEx.Country.MT.to_string()
+    "MT 84 MALT 01100 0012345MTLCAST001S"
+
   """
 
   @size 31