Adding revdepcheck Instructions to PR Template (#369)

**What changes are proposed in this pull request?**
* Style this entry in a way that can be copied directly into `NEWS.md`.
(#<issue number>, @<username>)

Provide more detail here as needed.

**Reference GitHub issue associated with pull request.** _e.g., 'closes
#<issue number>'_



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

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/PULL_REQUEST_TEMPLATE.md

@@ -26,3 +26,24 @@ When the branch is ready to be merged:
 - [ ] **All** GitHub Action workflows pass with a :white_check_mark:
 - [ ] Approve Pull Request
 - [ ] Merge the PR. Please use "Squash and merge" or "Rebase and merge".
+
+_Optional Reverse Dependency Checks_:
+
+- Install `checked` with `pak::pak("Genentech/checked")` or `pak::pak("checked")`
+- Check dev versions of `cardx`, `gtsummary`, and `tfrmt` which are in the `ddsjoberg` R Universe
+
+  ```shell
+  Rscript -e "options(checked.check_envvars = c(NOT_CRAN = TRUE)); checked::check_rev_deps(path = '.', repos = c('https://ddsjoberg.r-universe.dev', 'https://cloud.r-project.org'))"
+  ```
+
+- Check CRAN reverse dependencies but run tests skipped on CRAN
+
+  ```shell
+  Rscript -e "options(checked.check_envvars = c(NOT_CRAN = TRUE)); checked::check_rev_deps(path = '.', repos = 'https://cloud.r-project.org')"
+  ```
+
+- Check CRAN reverse dependencies in a CRAN-like environment
+
+  ```shell
+  Rscript -e "options(checked.check_envvars = c(NOT_CRAN = FALSE), checked.check_build_args = '--as-cran'); checked::check_rev_deps(path = '.', repos = 'https://cloud.r-project.org')"
+  ```