LibJS: Add the Temporal.now namespace object

This will be home to various functions:

- Temporal.now.timeZone()
- Temporal.now.instant()
- Temporal.now.plainDateTime()
- Temporal.now.plainDateTimeISO()
- Temporal.now.zonedDateTime()
- Temporal.now.zonedDateTimeISO()
- Temporal.now.plainDate()
- Temporal.now.plainDateISO()
- Temporal.now.plainTimeISO()

Userland/Libraries/LibJS/Runtime/Temporal/Now.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+
+namespace JS::Temporal {
+
+class Now final : public Object {
+    JS_OBJECT(Now, Object);
+
+public:
+    explicit Now(GlobalObject&);
+    virtual void initialize(GlobalObject&) override;
+    virtual ~Now() override = default;
+};
+
+}