Allow empty firstname in addContributor()

[ThierryO]

This is allowed in addCreator() (see #26)

Maybe simple change

zen4R/R/ZenodoRecord.R

Line 368 in 5fd44d5

contributor <- list(name = paste(lastname, firstname, sep=", "), type = type)

into

contributor <- list(name = paste(c(lastname, firstname), collapse=", "), type = type) 

A contributor can be an entity (e.g. organisation which is the copyright holder).

[eblondel]

@ThierryO i've pushed some code , let me know if it's ok

[ThierryO]

Thanks for the fast response. It works as expected.

I'm working on an upload function depending on a path containing a .zenodo.json. Maybe an idea to incorpate in zen4R?