Get access to core module

[ndt080]

Add support for accessing utilities from the core directory to the builder.
Example,

import { createVirtualStore } from 'virtua/core'

Goal:
To allow developers to implement their own Virtualizer component for unsupported platforms or complex implementations.

Add support for accessing utilities from the core directory to the builder. Such access, for example, is provided by tanstack packages

[inokawa]

Duplicate of #388