Add OPT-IML Checkpoints
### Model description

OPT-IML models are instruction-finetuned from the OPT checkpoints. Here is the [technical report](https://github.com/facebookresearch/metaseq/blob/main/projects/OPT-IML/optimal_paper_v1.pdf).

### Open source status

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

### Provide useful links for the implementation

* **Technical report:** https://github.com/facebookresearch/metaseq/blob/main/projects/OPT-IML/optimal_paper_v1.pdf
* **Model implementation:** same as OPT
* **Model weights:** https://github.com/facebookresearch/metaseq/tree/main/projects/OPT-IML
* **Authors:** Meta AI
🙏 <|||||>I tried to convert and also ran into this issue:

https://github.com/facebookresearch/metaseq/issues/567
https://github.com/facebookresearch/metaseq/issues/594

But it seems like meta folks are working to upload it to huggingface:

https://github.com/facebookresearch/metaseq/issues/567#issuecomment-1370415582<|||||>maybe I will tag @patrickvonplaten in case who I believe converted the last OPT checkpoints :-)<|||||>I believe it was @ArthurZucker <|||||>Thanks for bumping on this! <|||||>Also working on this, have run into the same issues mentioned above. Let me know if I can be an extra pair of eyes/hands for working on this.<|||||>Weights are available here thanks to (https://huggingface.co/rpasunuru) : 
- https://huggingface.co/facebook/opt-iml-30b
- https://huggingface.co/facebook/opt-iml-1.3b
Closing! 