Add support for NIST Public Data Reposity DOIs

[jat255]

This PR implements a DOI downloader for the NIST public data repository at https://data.nist.gov

This is my first attempt at developing on pooch at all, so please let me know if there are any changes needed, but I have included tests, and it is working so far as I can tell. Happy to iterate as needed.

Relevant issues/PRs:

Fixes #441

[jat255]

@santisoler is there anything else needed for this PR to get a review? (apologies if you're not the right ping, but I saw you had the most recent merge activity)

[santisoler]

Hi @jat255. Thanks for opening this PR. And yes, it's ok to ping me here.

Sorry for the delay. These past weeks were too busy for me.

I'll take a look at this and come back later. But again, thanks for taking the time to open this PR.

cc @leouieda

[santisoler]

In the meantime. Do you have a link to the API specification of the NIST data repository?

In order to makes our lives easier while maintaining this feature, it's important to have a reference of the responses that the API supports, so we can avoid relying on responses that might change in the future.

[jat255]

No worries. Thanks for the status update. The API information is here, though the request response is not particularly thoroughly specified, it appears: https://data.nist.gov/rmm/#/operations/record

I'll open a request with the team in charge of this project to see if they can fix that and get a better "example" response shown on that page. (EDIT: see usnistgov/oar-pdr#353 to track this)

To see an example response, you can enter a valid ID in the box on the page (such as mds2-3408) to see what the API returns.