Add citation info to PDF

Change-Id: Ic250ee6edc9149cf9ac816b911eea165d86ac71c
diff --git a/R/rderekovecs-package.R b/R/rderekovecs-package.R
index e6a755d..82585fd 100644
--- a/R/rderekovecs-package.R
+++ b/R/rderekovecs-package.R
@@ -1,4 +1,9 @@
-#' @keywords internal
+#' @references Type
+#' `citation(rderekovecs)`
+#' to see how to refer to this package
+#' @details Package version `r as.character(packageVersion("rderekovecs"))`
+#'
+#'
 "_PACKAGE"
 
 ## usethis namespace: start