[R-pkg-team] updating r-cran-v8 in experimental

[Jeroen Ooms]

Debian 'experimental' now has nodeJS v12.x which ships with a new
version of the v8 engine. In order to build r-cran-v8 against this
libnode, you need the latest version of the R package:
https://cran.r-project.org/web/packages/V8/index.html

Perhaps r-cran-v8 2.2 should be uploaded to experimental?

Also the description of the package has changed (a long time ago) so
perhaps this can be updated as well :)

Thanks!

Jeroen