support for reading scan files

[japhir]

What's the progress on reading in .scn files? On the old isoread repository, this was the one thing we could get into R using your nice collection of scripts! ;-).

I'm willing to help develop, but I first have to get how isoreader operates under the hood, and make the helper functions available to play around with (I guess I can copy your repo, set all the functions to @export and then I should be able to play around with them on my machine?).