[R] snapshot3d hangs during rmarkdown::render

[Duncan Murdoch]

I believe I have found and fixed a bug in webshot2 that was causing 
these problems.  My current recommendation for installing it is to use

   remotes::install_github("dmurdoch/webshot2 using fixlockup")

For more details (and a bug fix for pkgdown, if you're trying to put 
dynamic graphics on a pkgdown site) see

   https://github.com/dmurdoch/rgl#note-about-devel-versions

Duncan Murdoch