math/R-cran-metabook: New port: Data sets and code for "Meta-Analysis with R"

[longros]

Summary

Data sets and code for the book Meta-Analysis with R. Dependency of math/R-cran-meta.

Test Plan

poudriere testport passes in 144amd64, 145amd64 and 151

[jrm]

Since the commit message says "Dependency of math/R-cran-meta", I presume you will be committing that new port as well. Perhaps commit them at the same time?

[longros]

Update WWW to the new CRAN URL format