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

lib/iban_ex/country/cz.ex

@@ -1,6 +1,13 @@
 defmodule IbanEx.Country.CZ do
   @moduledoc """
   Czech Republic IBAN parsing rules
+
+  ## Examples
+
+    iex> %IbanEx.Iban{country_code: "CZ", check_digits: "65", bank_code: "0800", branch_code: nil, national_check: nil, account_number: "0000192000145399"}
+    iex> |> IbanEx.Country.CZ.to_string()
+    "CZ 65 0800 0000192000145399"
+
   """
 
   @size 24