Add HyenaDNA model
### Model description

HyenaDNA is a long-range genomic foundation model pretrained on context lengths of up to 1 million tokens at single nucleotide resolution.

I would like to add this model to the transformers.

### Open source status

- [X] The model implementation is available
- [X] The model weights are available

### Provide useful links for the implementation

Code: https://github.com/HazyResearch/hyena-dna
Weights: https://huggingface.co/LongSafari
Paper: https://arxiv.org/abs/2306.15794

cc @exnx
Hi @heytanay, thanks for opening this issue! 

The easiest and recommended way to make a model available in `transformers` is to add the modeling code directly on the hub: https://huggingface.co/docs/transformers/custom_models

This means, once working, the model can be found and used immediately without having to go through the PR process. We find this is a lot quicker as the bar for adding code into the library is high due to the maintenance cost of every new model, and so reviews take quite a while.

Let us know if you have any questions about how to add a model using this process. Looking forward to seeing this model in action! <|||||>Thanks for this @amyeroberts! I will proceed with that!<|||||>Hi, @heytanay we are also working on adding hyena models to transformers, how far along are you ?<|||||>@djaym7 As Amy mentioned, I won't be implementing the model directly in transformers and instead will be adding it directly to the hub. If you are doing it / already have done it, please go ahead!