LibJS: Start implementing Temporal.TimeZone

Here we got our first Temporal object :^)
This patch adds the TimeZone object itself, its constructor and
prototype (currently empty), and a bunch of required abstract operations

Userland/Libraries/LibJS/Runtime/Temporal/TimeZoneConstructor.cpp

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Temporal/ISO8601.h>
+#include <LibJS/Runtime/Temporal/TimeZone.h>
+#include <LibJS/Runtime/Temporal/TimeZoneConstructor.h>
+
+namespace JS::Temporal {
+
+// 11.2 The Temporal.TimeZone Constructor, https://tc39.es/proposal-temporal/#sec-temporal-timezone-constructor
+TimeZoneConstructor::TimeZoneConstructor(GlobalObject& global_object)
+    : NativeFunction(vm().names.TimeZone.as_string(), *global_object.function_prototype())
+{
+}
+
+void TimeZoneConstructor::initialize(GlobalObject& global_object)
+{
+    NativeFunction::initialize(global_object);
+
+    auto& vm = this->vm();
+
+    // 11.3.1 Temporal.TimeZone.prototype, https://tc39.es/proposal-temporal/#sec-temporal-timezone-prototype
+    define_direct_property(vm.names.prototype, global_object.temporal_time_zone_prototype(), 0);
+
+    define_direct_property(vm.names.length, Value(1), Attribute::Configurable);
+}
+
+// 11.2.1 Temporal.TimeZone ( identifier ), https://tc39.es/proposal-temporal/#sec-temporal.timezone
+Value TimeZoneConstructor::call()
+{
+    auto& vm = this->vm();
+
+    // 1. If NewTarget is undefined, then
+    // a. Throw a TypeError exception.
+    vm.throw_exception<TypeError>(global_object(), ErrorType::ConstructorWithoutNew, "Temporal.TimeZone");
+    return {};
+}
+
+// 11.2.1 Temporal.TimeZone ( identifier ), https://tc39.es/proposal-temporal/#sec-temporal.timezone
+Value TimeZoneConstructor::construct(FunctionObject& new_target)
+{
+    auto& vm = this->vm();
+    auto& global_object = this->global_object();
+
+    // 2. Set identifier to ? ToString(identifier).
+    auto identifier = vm.argument(0).to_string(global_object);
+    if (vm.exception())
+        return {};
+
+    String canonical;
+
+    // 3. If identifier satisfies the syntax of a TimeZoneNumericUTCOffset (see 13.33), then
+    if (is_valid_time_zone_numeric_utc_offset(identifier)) {
+        // TODO:
+        // a. Let offsetNanoseconds be ? ParseTimeZoneOffsetString(identifier).
+        // b. Let canonical be ! FormatTimeZoneOffsetString(offsetNanoseconds).
+    }
+    // 4. Else,
+    else {
+        // a. If ! IsValidTimeZoneName(identifier) is false, then
+        if (!is_valid_time_zone_name(identifier)) {
+            // i. Throw a RangeError exception.
+            vm.throw_exception<RangeError>(global_object);
+            return {};
+        }
+
+        // b. Let canonical be ! CanonicalizeTimeZoneName(identifier).
+        canonical = canonicalize_time_zone_name(identifier);
+    }
+
+    // 5. Return ? CreateTemporalTimeZone(canonical, NewTarget).
+    return create_temporal_time_zone(global_object, canonical, &new_target);
+}
+
+}