Request: Hosting R package in R-universe

Catboost has an R version, but this version is not currently in CRAN (the R package repository). Installing it is very inconvenient, as right now the only reliable way of doing so is by either manually downloading a compressed file from the GitHub releases page and using `R CMD INSTALL`, or by building it from source by cloning the repo (R install instructions from the docs do not work due to timeout, unless one has a very fast connection and is located nearby a yandex server).

ROpenSci has now launched the [R-universe](https://ropensci.org/r-universe/) package repository, which doesn't have so strict requirements for packages as CRAN. Catboost uses its own build system and follows code practices which would disquality it from being accepted at CRAN, but it could still be hosted as an installable package in R-universe.

Would be nice to see catboost getting its R releases there, so that it could be installed easily with `install.packages` from R and so that its R documentation would be easily browsable.