add rmarkdown to suggests (#4605)
add rmarkdown to suggests (#4605)


vlulla/data.table,jangorecki/data.table,vlulla/data.table,Rdatatable/data.table,Rdatatable/data.table,jangorecki/data.table,vlulla/data.table,vlulla/data.table,jangorecki/data.table,Rdatatable/data.table,jangorecki/data.table,Rdatatable/data.table