fix(heap, readme): MemoryAllocator => Heap, update readme

kernel/src/Memory/Heap.cpp

@@ -4,7 +4,7 @@
     * Copyright (c) 2025 Daniel Hammer
 */
 
-#include "MemoryAllocator.hpp"
+#include "Heap.hpp"
 #include "Memmap.hpp"
 #include "HHDM.hpp"
 

kernel/src/Memory/Memmap.cpp

@@ -2,7 +2,7 @@
 #include <Terminal/terminal.hpp>
 #include <Common/Panic.hpp>
 
-#include "MemoryAllocator.hpp"
+#include "Heap.hpp"
 
 using namespace Kt;