Allow integers in numeric class checks

[edelarua]

What changes are proposed in this pull request?

• When checking that the class of a value is numeric, also allow integers.

Closes #1867

---

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

• Ensure all package dependencies are installed: renv::install()
• 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 into master:

• Update NEWS.md with the changes from this pull request under the heading "# gtsummary (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".

[ddsjoberg]

Thank you @edelarua for the quick fix!! 🙇🏼‍♂️

Can we add one unit test, then we can go ahead and merge?

[edelarua]

@ddsjoberg unit test added :)

[ddsjoberg]

Looks great, thank you @edelarua !!