[R-package] add new copyright holder in DESCRIPTION (#3409)

* [R-package] add new copyright holder in DESCRIPTION

* fix role

R-package/DESCRIPTION

@@ -7,7 +7,8 @@ Authors@R: c(
     person("Guolin", "Ke", email = "guolin.ke@microsoft.com", role = c("aut", "cre")),
     person("Damien", "Soukhavong", email = "damien.soukhavong@skema.edu", role = c("aut")),
     person("Yachen", "Yan", role = c("ctb")),
-    person("James", "Lamb", email="jaylamb20@gmail.com", role = c("aut"))
+    person("James", "Lamb", email="jaylamb20@gmail.com", role = c("aut")),
+    person("IBM Corporation", role = c("ctb"))
     )
 Description: Tree based algorithms can be improved by introducing boosting frameworks. 'LightGBM' is one such framework, and this package offers an R interface to work with it.
     It is designed to be distributed and efficient with the following advantages: