LibJS: Add the Map built-in object

Userland/Libraries/LibJS/Runtime/Map.cpp

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/Map.h>
+
+namespace JS {
+
+Map* Map::create(GlobalObject& global_object)
+{
+    return global_object.heap().allocate<Map>(global_object, *global_object.map_prototype());
+}
+
+Map::Map(Object& prototype)
+    : Object(prototype)
+{
+}
+
+Map::~Map()
+{
+}
+
+void Map::visit_edges(Cell::Visitor& visitor)
+{
+    Object::visit_edges(visitor);
+    for (auto& value : m_entries) {
+        visitor.visit(value.key);
+        visitor.visit(value.value);
+    }
+}
+
+}