Add TinValid::COUNTRY_CODES

Author: sunny

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## [Unreleased]
 
+Features:
+- Add `TinValid::COUNTRY_CODES` to get available country codes.
+
 Fixes:
 - Fix Bulgaria to accept TINs starting with `10` instead of `00` 🇧🇬
 - Fix Finland checks for tins ending in `P` 🇫🇮

lib/tin_valid.rb

@@ -33,4 +33,35 @@
 require_relative "tin_valid/sweden_tin"
 require_relative "tin_valid/united_kingdom_tin"
 
-module TinValid; end
+module TinValid
+  COUNTRY_CODES = %w[
+    at
+    be
+    bg
+    cy
+    cz
+    de
+    dk
+    ee
+    es
+    fi
+    fr
+    gb
+    gr
+    hr
+    hu
+    ie
+    it
+    lt
+    lu
+    lv
+    mt
+    nl
+    pl
+    pt
+    ro
+    se
+    si
+    sk
+  ].freeze
+end