Use \describe with \item{}{} for list

[eddelbuettel]

Closes #2

This changed the markdown style list in the help for ?document to \describe{} with `\item{label{longer description} which makes it

     namespace: How to handle NAMESPACE generation. One of

          "overwrite" Fully regenerate NAMESPACE (default)

          "append" Insert between ## rhydrogen start/end markers

          "none" Don't modify NAMESPACE

[TroyHernandez]

Merged with rebase onto main (after rename). Thanks Dirk!