Add an isolated functional testing mechanism

[GPortas]

Overview of the feature request

Add a functional testing mechanism for the use cases of the package that helps in the review and QA process of the PRs, so that the use cases can be tested in isolation, without having to depend on other repositories like the dataverse-frontend to prove that the use cases consumption works from a functional perspective.

These tests would help to verify that use cases can be imported with no issues, as stated in this comment: #116 (comment)

What inspired the request?

Retrospective action item.

What existing behavior do you want changed?

None

Any brand new behavior do you want to add to js-dataverse?

None

Any open or closed issues related to this feature request?

None