Add support for the R language

[rpodcast]

Finally getting to filing a proper issue based on previous discussions on the Discord flakehub channel: It would be great to have support for initializing projects based in the R language used for statistical and data science computing. I've inspected the python handler for inspiration, and it looks like a lot of the same principles could be lifted in this handler:

• Choice of R version: Current stable version is 4.3.3. As for previous versions to offer, they could either be the point releases in the 4.3 branch, or the latest point releases in the minor versions. I'm inclined to say the latter, hence the previous version choices could be 4.2.3, 4.1.3, and 4.0.5,
• Tools for package reproducibility: Similar to the Python environment tools like virtualenv and pipenv, the R language has a package called {renv}[https://rstudio.github.io/renv/articles/renv.html] that provides similar functionality.
• I'm on the fence regarding offering the user a set of additional R packages to start their project with. I see that the python handler doesn't offer any additional python packages besides the aforementioned environment tools. In more data science projects, the tidyverse suite of packages are quite popular, however they are not a one-size-fits-all as there are many alternative packages for data processing, and base R itself already includes functionality for data analysis. The biggest issue I see is that many of the packages in the tidyverse contain C++ code, hence would require compilation.

The typical file types indicating an R project would be files ending in the following extensions: .R, .r, .Rmd, ,rmd. Also, a plain text file called DESCRIPTION indicates the source code for an R package.