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

lib/iban_ex/country/gi.ex

@@ -0,0 +1,17 @@
+defmodule IbanEx.Country.GI do
+  @moduledoc """
+  Gibraltar IBAN parsing rules
+
+  ## Examples
+
+    iex> %IbanEx.Iban{country_code: "GI", check_digits: "75", bank_code: "NWBK", branch_code: nil, national_check: nil, account_number: "000000007099453"}
+    iex> |> IbanEx.Country.GI.to_string()
+    "GI 75 NWBK 000000007099453"
+
+  """
+
+  @size 23
+  @rule ~r/^(?<bank_code>[A-Z]{4})(?<account_number>[0-9A-Z]{15})$/i
+
+  use IbanEx.Country.Template
+end