AK: Add UnicodeUtils with Unicode-related helper functions

This introduces the UnicodeUtils file, which contains helper functions
related to Unicode. This is in contrast to StringUtils, whose functions
are not directly related to Unicode and are, in theory,
encoding-agnostic.

AK/UnicodeUtils.h

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2021, Max Wipfli <mail@maxwipfli.ch>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+
+namespace AK::UnicodeUtils {
+
+constexpr bool is_unicode_control_code_point(u32 code_point)
+{
+    return code_point < 0x20 || (code_point >= 0x80 && code_point < 0xa0);
+}
+
+Optional<StringView> get_unicode_control_code_point_alias(u32);
+
+}