Add Donut
# What does this PR do?

This PR adds Donut to the library. Donut is to LayoutLM what T5 is to BERT. :D 

The model is implemented as an instance of our existing `VisionEncoderDecoderModel`.

See also https://github.com/clovaai/donut/issues/10#issue-1324734927

To do:

- [x] move repos to appropriate organization in
- [x] update niels to appropriate organization in `test_modeling_vision_encoder_decoder.py`
_The documentation is not available anymore as the PR was closed or merged._<|||||>I have implemented a new `DonutSwinModel`, that copies everything of `SwinModel`, except the final layer norm. I've added it in a file called `modeling_donut_swin.py` (and implemented a corresponding `DonutSwinConfig` in `configuration_donut_swin.py`). 

I went with `modeling_donut_swin.py` (and `configuration_donut_swin.py`) in the "donut" folder rather than `modeling_donut.py` (and `configuration_donut.py`) since it only implements the model and configuration of the encoder part (Swin Transformer). For the decoder, BART is leveraged. Let me know if this is ok.<|||||>Hi @NielsRogge , do you plan on supporting: `Document Parsing` modality? 