update ard_cohens_d function to accept multiple variables

[ayogasekaram]

What changes are proposed in this pull request?
update ard_cohens_d and ard_paired_cohens_d functions to accept multiple variables

closes #85

---

Pre-review Checklist (if item does not apply, mark is as complete)

• All GitHub Action workflows pass with a ✅
• 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.
• Code coverage is suitable for any new functions/features (generally, 100% coverage for new code): devtools::test_coverage()
• Request a reviewer

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

• 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()

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).
• All GitHub Action workflows pass with a ✅
• Approve Pull Request
• Merge the PR. Please use "Squash and merge" or "Rebase and merge".

[github-actions]

Code Coverage Summary

Filename                    Stmts    Miss  Cover    Missing
------------------------  -------  ------  -------  ------------------------------------
R/ard_car_anova.R              41       2  95.12%   57, 60
R/ard_chisqtest.R              31       0  100.00%
R/ard_cohens_d.R               87       2  97.70%   64, 107
R/ard_fishertest.R             33       0  100.00%
R/ard_hedges_g.R               60       0  100.00%
R/ard_kruskaltest.R            27       0  100.00%
R/ard_mcnemartest.R            41       0  100.00%
R/ard_moodtest.R               40       0  100.00%
R/ard_proportion_ci.R          40       5  87.50%   63-67
R/ard_proptest.R               71       0  100.00%
R/ard_regression_basic.R       14       1  92.86%   44
R/ard_regression.R             49       0  100.00%
R/ard_smd.R                    40       0  100.00%
R/ard_ttest.R                  78       0  100.00%
R/ard_vif.R                    58       2  96.55%   46, 80
R/ard_wilcoxtest.R             97       2  97.94%   61, 103
R/proportion_ci.R             188      28  85.11%   275, 278, 287-292, 300, 315, 415-438
TOTAL                         995      42  95.78%

Diff against main

Filename            Stmts    Miss  Cover
----------------  -------  ------  -------
R/ard_cohens_d.R      +14      +2  -2.30%
TOTAL                 +14      +2  -0.14%

Results for commit: e7493c8

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

 1 files  29 suites   4s ⏱️
28 tests 20 ✅  8 💤 0 ❌
71 runs  52 ✅ 19 💤 0 ❌

Results for commit e7493c8.

♻️ This comment has been updated with latest results.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.93939% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 98.95%. Comparing base (eb2b89f) to head (6c6f102).
Report is 1 commits behind head on main.

❗ Current head 6c6f102 differs from pull request most recent head e7493c8. Consider uploading reports for the commit e7493c8 to get more accurate results

Files	Patch %	Lines
R/ard_cohens_d.R	93.93%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #87      +/-   ##
==========================================
- Coverage   99.17%   98.95%   -0.23%     
==========================================
  Files          17       17              
  Lines         848      858      +10     
==========================================
+ Hits          841      849       +8     
- Misses          7        9       +2     

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[ddsjoberg]

Thank you for this PR!! ⭐ ⭐ ⭐