Add rtools and add registry for R

[Yunuuuu]

Thanks for the scoop bucket repo.

This commit should resolve #30, Note that the same issue reported in Positron also exists in RStudio.

Additionally, this commit adds support for Rtools 40–44 for R versions > 4.0.0.

• From R 4.2.0 onward, R inspects the environment variable RTOOLS42_HOME.
• From R 4.3.0, it inspects RTOOLS43_HOME.
• From R 4.4.0, it inspects RTOOLS44_HOME.

As a result, rtools42, rtools43, and rtools44 now set their respective environment variables.

For R versions ≥ 4.0.0 and < 4.2.0, r-release will create Renviron.site and add: PATH="${RTOOLS40_HOME-C:/rtools40}/usr/bin;${PATH}". This follows the same approach as R ≥ 4.2.0. So rtools40 also sets RTOOLS40_HOME.

My original R manifest was based on yours (should be R version 3.5), and I’ve maintained my own Scoop bucket repo at https://github.com/Yunuuuu/jade. I have used these configurations on multiple computers in my labs and for my senior and junior labmates (from R 3.5 to the latest version), and they have worked well.

I hope these improvements enhance the official R bucket repo!