[Feature] Export as 3MF

[khionu]

To be frank, I have no idea how big of an ask this is, but it would be nice if it were possible to use Fidget to export printable files.

https://en.wikipedia.org/wiki/3D_Manufacturing_Format

[ChrisChrisLoLo]

Out of curiosity, Is there anything specific that you'd want from the 3MF file over STL?