LibJS: Implement a nearly empty Intl.Collator object

This adds plumbing for the Intl.Collator object, constructor, and
prototype.

Userland/Libraries/LibJS/Runtime/Intl/Collator.h

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@pm.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Array.h>
+#include <AK/String.h>
+#include <AK/StringView.h>
+#include <LibJS/Runtime/Object.h>
+
+namespace JS::Intl {
+
+class Collator final : public Object {
+    JS_OBJECT(Collator, Object);
+
+public:
+    enum class Usage {
+        Sort,
+        Search,
+    };
+
+    enum class Sensitivity {
+        Base,
+        Accent,
+        Case,
+        Variant,
+    };
+
+    enum class CaseFirst {
+        Upper,
+        Lower,
+        False,
+    };
+
+    static constexpr auto relevant_extension_keys()
+    {
+        // 10.2.3 Internal Slots, https://tc39.es/ecma402/#sec-intl-collator-internal-slots
+        // The value of the [[RelevantExtensionKeys]] internal slot is a List that must include the element "co", may include any or all of the elements "kf" and "kn", and must not include any other elements.
+        return AK::Array { "co"sv, "kf"sv, "kn"sv };
+    }
+
+    explicit Collator(Object& prototype);
+    virtual ~Collator() override = default;
+
+    String const& locale() const { return m_locale; }
+    void set_locale(String locale) { m_locale = move(locale); }
+
+    Usage usage() const { return m_usage; }
+    void set_usage(StringView usage);
+    StringView usage_string() const;
+
+    Sensitivity sensitivity() const { return m_sensitivity; }
+    void set_sensitivity(StringView sensitivity);
+    StringView sensitivity_string() const;
+
+    CaseFirst case_first() const { return m_case_first; }
+    void set_case_first(StringView case_first);
+    StringView case_first_string() const;
+
+    String const& collation() const { return m_collation; }
+    void set_collation(String collation) { m_collation = move(collation); }
+
+    bool ignore_punctuation() const { return m_ignore_punctuation; }
+    void set_ignore_punctuation(bool ignore_punctuation) { m_ignore_punctuation = ignore_punctuation; }
+
+    bool numeric() const { return m_numeric; }
+    void set_numeric(bool numeric) { m_numeric = numeric; }
+
+private:
+    String m_locale;                                    // [[Locale]]
+    Usage m_usage { Usage::Sort };                      // [[Usage]]
+    Sensitivity m_sensitivity { Sensitivity::Variant }; // [[Sensitivity]]
+    CaseFirst m_case_first { CaseFirst::False };        // [[CaseFirst]]
+    String m_collation;                                 // [[Collation]]
+    bool m_ignore_punctuation { false };                // [[IgnorePunctuation]]
+    bool m_numeric { false };                           // [[Numeric]]
+};
+
+}