Add R test action

[jared321]

As part of the upcoming release we will manually test the R wrapper to confirm that it functions correctly. Before work continues in this repository, a GitHub action should be set up to test the R wrapper.

Some sites that might provide useful information

• https://rguides.dev/guides/r-github-actions-r/
• https://www.r-bloggers.com/2025/02/checking-your-r-packages-and-practicals-on-a-schedule-using-github-actions
• https://github.com/r-lib/actions