Add mmap allocator

src/platform.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <stdlib.h>
+
+void *platform_malloc(size_t sz);
+void platform_free(void *mem);
+
+void *memory_allocate(size_t sz);
+void *memory_free(void *mem, size_t sz);