Add GPT-SW3 models to huggingface
### Model description

At AI Sweden we are developing GPT models for the nordic region. Languages include English, Swedish, Danish, Norwegian and Icelandic. 
The models are of the GPT family.
The models will range in size from 126m to 20B.
They are trained from scratch on a large corpora of 320B tokens.
They are trained with the nemo megatron framework and has a sentencepiece tokenizer.
The weights are not shared yet and we intend to share them through huggingface as well as publishing our training process and results.

### Open source status

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

### Provide useful links for the implementation

Training framework: https://developer.nvidia.com/nemo/megatron
PR merged! :partying_face: 