LibJS: Add DisposableStack{, Prototype, Constructor}

Since the async parts of the spec are not stage 3 at this point we don't
add AsyncDisposableStack.

Userland/Libraries/LibJS/Runtime/DisposableStackConstructor.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2022, David Tuin <davidot@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/NativeFunction.h>
+
+namespace JS {
+
+class DisposableStackConstructor final : public NativeFunction {
+    JS_OBJECT(DisposableStackConstructor, NativeFunction);
+
+public:
+    virtual void initialize(Realm&) override;
+    virtual ~DisposableStackConstructor() override = default;
+
+    virtual ThrowCompletionOr<Value> call() override;
+    virtual ThrowCompletionOr<NonnullGCPtr<Object>> construct(FunctionObject&) override;
+
+private:
+    explicit DisposableStackConstructor(Realm&);
+
+    virtual bool has_constructor() const override { return true; }
+};
+
+}