update ard_fischertest() to accept multiple vars

[ayogasekaram]

What changes are proposed in this pull request?
update ard_fischertest() to accept multiple vars

closes #92

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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              38       1  97.37%   37
R/ard_cohens_d.R               87       2  97.70%   64, 107
R/ard_fishertest.R             40       1  97.50%   37
R/ard_hedges_g.R               75       2  97.33%   63, 106
R/ard_kruskaltest.R            27       0  100.00%
R/ard_mcnemartest.R            41       0  100.00%
R/ard_moodtest.R               47       1  97.87%   44
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                    47       0  100.00%
R/ard_svychisq.R               36       1  97.22%   42
R/ard_svycontinuous.R         192       2  98.96%   166, 176
R/ard_svyttest.R               49       0  100.00%
R/ard_ttest.R                  92       2  97.83%   61, 103
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                        1329      52  96.09%

Diff against main

Filename              Stmts    Miss  Cover
------------------  -------  ------  -------
R/ard_fishertest.R       +7      +1  -2.50%
TOTAL                    +7      +1  -0.05%

Results for commit: 5d3da7a

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

  1 files  40 suites   6s ⏱️
 39 tests 29 ✅ 10 💤 0 ❌
117 runs  94 ✅ 23 💤 0 ❌

Results for commit 5d3da7a.

♻️ This comment has been updated with latest results.

[ddsjoberg]

‧₊˚❀༉‧₊˚. lovely ‧₊˚❀༉‧₊˚.

thank you!