Document `subclass` parameter of `roclet()`

[maelle]

roxygen2/R/roclet.R

Line 38 in 145e7b4

roclet <- function(subclass, ...) {

It should be a character vector (vector: https://github.com/gaborcsardi/roxygenlabs/blob/5a7e4449c28f9e423de3f4e8e1be9bc9080f4e52/R/roclet.R#L15)