LightGBM

[R-package] Add R logo (fixes #3331, #3332) (#3336)

* [R-package] add R package logo

* more changes

* add logo in the place CRAN expects

* revert unnecessary Rbuildignore stuff

* uploaded hex logo for R-package in SVG format (#3340)

* remove duplicate logo and fix CI

* use SVG instead of PNG

Co-authored-by: Nikita Titov <nekit94-08@mail.ru>