[Feature] Add support for Donut (Multimodal Model)

[WaterKnight1998]

Thank you very much for sharing this library, it is going to be very useful for fine tuning big models.

It would be cool if Donut model is supported. This model works very well for key information extraction from document images. ;)

Could you share an example on how to use it with this model?

Thanks in advance! @NielsRogge