Add thumbnail support for 3D and PDF files

[ioeylim]

Briefly spoke to Salief about this earlier, but noticed that the default fallback thumbnail for items doesn't look as nice on the grid view (largely due to how big it becomes). This could be addressed by stylizing the fallback to be more icon-based, but feel like there is more thumbnail support we could do first for 3d and pdf files.

cc: @salieflewis

[0xTranqui]

theres def some "screenshot' github libraries we could prob add into our flow that would make this super trivial

[0xTranqui]

btw @salieflewis just checking in on priortization. can we please NOT prioritize this before getting things in like full site routing, view pages, etc

[ioeylim]

video thumbnails partially tackled with #512 and #513

removing "video" from this issue