added deit onnx config
Author: 0xrushi
Pull request: yes

# What does this PR do?

Added DeiT OnnxConfig to make this model available for conversion

@ChainYo 

https://github.com/huggingface/transformers/issues/16308

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

> # What does this PR do?
> Added DeiT OnnxConfig to make this model available for conversion
> 
> @ChainYo

> ## Who can review?
> Anyone in the community is free to review the PR once the tests have passed. Feel free to tag members/contributors who may be interested in your PR.


Also pinging @LysandreJik, @lewtun  and @NielsRogge because he did the implementation of DeiT.


Btw Did you try to convert one `DeiT` model with your add ?
If so you could add the converted model to the [ONNXConfig for all](https://huggingface.co/OWG) organization, it would be awesome!

Thanks @lewtun , I just added those.

I'm trying to add a README  to [ONNXConfigForAll](https://huggingface.co/OWG),

How does onnx work in ViT? 
I tried the code below, but its not working

```
from transformers import ViTFeatureExtractor, ViTModel
import torch
from datasets import load_dataset
from onnxruntime import InferenceSession


dataset = load_dataset("huggingface/cats-image")
image = dataset["test"]["image"][0]

feature_extractor = ViTFeatureExtractor.from_pretrained("google/vit-base-patch16-224-in21k")
model = ViTModel.from_pretrained("google/vit-base-patch16-224-in21k")

inputs = feature_extractor(image, return_tensors="pt")

session = InferenceSession("onnx/model.onnx")

# ONNX Runtime expects NumPy arrays as input
outputs = session.run(output_names=["last_hidden_state"], input_feed=list(inputs))
```

> How does onnx work in ViT?
> I tried the code below, but its not working

Could you check on [netron.app](https://netron.app) what are the inputs of the onnx converted model and then check if the `input_feed` is correct. Btw it should be a `Dict` not a `List`.




> > How does onnx work in ViT?
> > I tried the code below, but its not working
> 
> Could you check on [netron.app](https://netron.app) what are the inputs of the onnx converted model and then check if the `input_feed` is correct. Btw it should be a `Dict` not a `List`.

And inputs itself is a dictionary
![image](https://user-images.githubusercontent.com/6279035/164775874-cfb14338-9893-4a28-b617-69358ff18aa3.png)


The input as seen from netron is pixel_values, I did try dict(inputs), inputs, list(inputs)

![image](https://user-images.githubusercontent.com/6279035/164775617-7381603a-4675-4ee8-88c6-91ceaff73ab3.png)


I just figured it out. You can find it here [https://huggingface.co/OWG/DeiT](https://huggingface.co/OWG/DeiT) :-)

> I just figured it out. You can find it here https://huggingface.co/OWG/DeiT :-)

It seems really good! :hugs: 

Thanks for the fix!