Add R CMD check results to release workflow

[pdil]

The PR published by @usmap-bot after running release.yaml should include the final R CMD Check results with "_R_CHECK_CRAN_INCOMING_" = "true" and --as-cran set so the maintainer(s) can review the check results as though they were run by CRAN to ensure all possible issues have been resolved before submission.

This will involve use of the r-lib/actions/check-r-package action and parsing out the check results to be included in the release-pr-body.md template.