reorganize pkgdown (#122)

**What changes are proposed in this pull request?**
pkgdown reorganization, divide `ard_*()` based on package 

preview: 
<img width="458" alt="image"
src="https://github.com/insightsengineering/cardx/assets/73252787/591e4193-7e74-4e99-aade-3a6e026f5cdc">


closes #114 


--------------------------------------------------------------------------------

Pre-review Checklist (if item does not apply, mark is as complete)
- [x] **All** GitHub Action workflows pass with a ✅
- [x] PR branch has pulled the most recent updates from master branch:
`usethis::pr_merge_main()`
- [x] If a bug was fixed, a unit test was added.
- [x] If a new `ard_*()` function was added, it passes the ARD
structural checks from `cards::check_ard_structure()`.
- [x] Code coverage is suitable for any new functions/features
(generally, 100% coverage for new code): `devtools::test_coverage()`

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

- [ ] If a bug was fixed, a unit test was added.
- [ ] 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 "`# cardx (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".

---------

Co-authored-by: Daniel Sjoberg <[email protected]>

_pkgdown.yml

@@ -22,10 +22,9 @@ authors:
 
 reference:
   - title: "ARD Creation"
-  - subtitle: "Inference"
+
+  - subtitle: "{stats} package"
   - contents:
-      - ard_aod_wald_test
-      - ard_car_anova
       - ard_stats_anova
       - ard_stats_aov
       - ard_stats_chisq_test
@@ -37,21 +36,41 @@ reference:
       - ard_stats_prop_test
       - ard_stats_t_test
       - ard_stats_wilcox_test
-      - ard_survey_svychisq
-      - ard_survey_svyranktest
-      - ard_survey_svyttest
 
-  - subtitle: "Estimation"
+  - subtitle: "{aod} package"
+  - contents:
+      - ard_aod_wald_test
+
+  - subtitle: "{car} package"
   - contents:
+      - ard_car_anova
       - ard_car_vif
+
+  - subtitle: "{effectsize} package"
+  - contents:
       - ard_effectsize_cohens_d
       - ard_effectsize_hedges_g
+
+  - subtitle: "{smd} package"
+  - contents:
+      - ard_smd_smd
+
+  - subtitle: "{survey} package"
+  - contents:
+      - ard_survey_svychisq
+      - ard_survey_svycontinuous
+      - ard_survey_svyranktest
+      - ard_survey_svyttest
+
+  - subtitle: "{survival} package"
+  - contents:
+    - ard_survival_survfit
+
+  - subtitle: "Other ARD functions"
+  - contents:
       - ard_proportion_ci
       - ard_regression
       - ard_regression_basic
-      - ard_smd_smd
-      - ard_survival_survfit
-      - ard_survey_svycontinuous
 
   - title: "Helpers"
   - contents: