Trigger R CMD check with dispatch

Description

Update to allow R CMD check to be triggered manually with workflow dispatch.

[x] This PR does NOT contain PHI or germline genetic data. A repo may need to be deleted if such data is uploaded. Disclosing PHI is a major problem.
[x] This PR does NOT contain molecular files, compressed files, output files such as images (e.g. .png, .jpeg), .pdf, .RData, .xlsx, .doc, .ppt, or other non-plain-text files. To automatically exclude such files using a .gitignore file, see here for example.
[x] I have read the code review guidelines and the code review best practice on GitHub check-list.
[x] I have set up or verified the main branch protection rule following the github standards before opening this pull request.
[x] The name of the branch is meaningful and well formatted following the standards, using [AD_username (or 5 letters of AD if AD is too long)]-[brief_description_of_branch].
[x] I have added the major changes included in this pull request to the NEWS under the next release version or unreleased, and updated the date. I have also updated the version number in DESCRIPTION according to semantic versioning rules.
[x] Both R CMD build and R CMD check run successfully.