feat: support RefObject for useScrollSpy scrollHost

[deshna1810]

Summary

This PR adds support for passing a React RefObject as the scrollHost option to useScrollSpy, in addition to the existing HTMLElement support.

Changes

• Extended the scrollHost type to accept HTMLElement | RefObject<HTMLElement | null>.
• Resolved the underlying DOM element internally when a ref is provided.
• Preserved the existing behavior for HTMLElement inputs, ensuring full backward compatibility.
• Updated the hook implementation to work seamlessly with React refs.
• Added/updated tests to cover both HTMLElement and RefObject usage.

Motivation

Previously, scrollHost only accepted a resolved HTMLElement, which made using React refs awkward because ref.current is null during the initial render and doesn't trigger a re-render when populated. Supporting RefObject provides a more idiomatic React API and removes the need for callback ref or state-based workarounds while maintaining existing functionality.