fix: update StepNavigationItem interface, resolves #546

[skorekm]

Closes @wfp/designsystem#546

The typescript interface for the StepNavigationItem is missing a page prop. Also, the renderAnchor prop is not optional as it's supposed to be.

Changelog

Changed

• page prop for the StepNavigationItem
• optional renderAnchor props for the StepNavigationItem

Removed

• value keyword from the import definitions in the index.d.ts file