Could we set the files being rendered with rmdv2 ?

[statquant]

Right now rmdv2 build only Rmd files. I think it would be great we could render .R instead (I use .R files that I render because I like the way I can run source on the file). It might just be adding a pattern argument to rmdv2 that would default to ".Rmd". Would you accept a PR for this ?

[yihui]

Yes, please. Thank you!