Add support for 3DM file previews

[dsonck92]

In my creative work, I use Rhino3D a lot. Under Windows, Rhino3D actually has preview support in Explorer. After diving into this a bit, there's a rough code snippet that details how this thumbnail works: https://developer.rhino3d.com/guides/cpp/extracting-thumbnail-preview-images/

From what I see, ON refers to "OpenNurbs" which is some initiative by them to make 3DM files more universally accepted. I think it could be nice to use this to try and extract a preview for the conversion project.

I want to see if I can actually get this into the conversion service myself. It seems like this library should also compile under Linux. Or otherwise, the limited scope of the functions needed might be portable somehow.