Visually differentiate child data packages from parents in nested datasets

[robyngit]

With the new hierarchical file display, it's not as clear that child datasets are separate from their parents.

See for example:

from https://arcticdata.io/catalog/view/urn%3Auuid%3Ad52bbb10-6f42-4b48-bbf9-986e10b53858

As reported by researchers, this could lead to the parent dataset being incorrectly cited rather than the child.

This task involves making the child datasets in nested packages more visually separate. We should find a way to indicate that these datasets have their own DOI and their own author list.

Related: https://github.com/NCEAS/metacatui/issues/2418

[robyngit]

Here is how the nested datasets looked before: