Add release type for R packages

[jolars]

It would be nice to have a release-type for R packages as well.

It should update the following files, I think:

• NEWS.md. This is basically the same as CHANGELOG.md. Technically you can write this as a NEWS file too, but I believe almost everyone uses NEWS.md with markdown syntax today.
• DESCRIPTION. There is a Version: x field. Here's some more information about the syntax of the file: https://cran.r-project.org/doc/manuals/R-exts.html#The-DESCRIPTION-file).

[chingor13]

We would be willing to take a PR to support these file updates as it looks like there's a defined structure for an R extension.