LibUnicode: Add some data related to currency codes

This data is published under ISO-4217 as an XML file. Since we can't
parse XML files yet, and the data isn't very large, it was translated to
C++ manually here.

Userland/Libraries/LibUnicode/CurrencyCode.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2021, Tim Flynn <trflynn89@pm.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <AK/Optional.h>
+#include <AK/StringView.h>
+
+namespace Unicode {
+
+struct CurrencyCode {
+    Optional<int> minor_unit {};
+};
+
+Optional<CurrencyCode> get_currency_code(StringView currency);
+
+}