Added ard_hierarchical() and ard_hierarchical_count()

[ddsjoberg]

What changes are proposed in this pull request?

• Added ard_hierarchical() and ard_hierarchical_count()

Reference GitHub issue associated with pull request. e.g., 'closes #1'
closes #54

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Reviewer Checklist (if item does not apply, mark is as complete)

• Ensure all package dependencies are installed: devtools::install_dev_deps()
• PR branch has pulled the most recent updates from master branch: usethis::pr_merge_main()
• If a bug was fixed, a unit test was added.
• Run pkgdown::build_site(). Check the R console for errors, and review the rendered website.
• Code coverage is suitable for any new functions/features: devtools::test_coverage()
• usethis::use_spell_check() runs with no spelling errors in documentation

When the branch is ready to be merged:

• Update NEWS.md with the changes from this pull request under the heading "# cards (development version)". If there is an issue associated with the pull request, reference it in parentheses at the end update (see NEWS.md for examples).
• Increment the version number using usethis::use_version(which = "dev")
• Run usethis::use_spell_check() again
• Approve Pull Request
• Merge the PR. Please use "Squash and merge".

[bzkrouse]

Great addition!!! Just 1 small request - it would be super helpful if there was something in the docs about how ard_hierarchical_count() computes results for all variables, and ard_hierarchical only computes results for the lowest level variable. Would it be possible to add that? Approving this as I don't need to review again :)

[ddsjoberg]

@bzkrouse ah yes! Great point :)