Add documentation for quarto_args of quarto_render()

[olivroy]

I had the same issue as the one mentioned in #81, but discovered late that I could do this.

I tried to find a place on the https://quarto.org website where they are all listed and documented, but I couldn't.

So I added a reference to the terminal, where we can find the options with

quarto render --help

Needs devtools::document()

Adds an example that makes it more obvious that you can render to an output-dir with quarto_render()

[olivroy]

Oops. Actually, this doesn't really work as I expect it. using this option deletes everything in the directory.

Would it be possible for Quarto to error if --output-dir is supplied on a document (as opposed to a project)

Or another solution would be that setting -output-dir does not delete the directory if rendering a file (as opposed to a project)

Maybe being able to supply output-file as a dir/file-name.ext would be great, but it currently doesn't work either.

[cderv]

I added the information to the help page.

For the rest, it is something to report in quarto-cli repo, but I believe we already have discussion about that.

Thanks !