chore: change knobs type to object where appropriate

It looks like, when a knob needs to pass an array of objects to a component, we can't use the [array knob type](uhttps://github.com/storybookjs/storybook/tree/master/addons/knobs#array which is only suitable for arrays of strings according to the doc.

The stories for Breadcrumb and InfiniteScroll components both use array knobs for array of objects, which seems to make those knobs unusable:

This MR fixes that by using the object knob type instead: