Add Restormer
### Model description

**Restormer: Efficient Transformer for High-Resolution Image Restoration** was published in CVPR 2022, which introduced a new Vision Transformer based architecture for Image Restoration tasks like Deraining, Motion Deblurring, Defocus Deblurring and Denoising. It reduced the time complexity of Self Attention in Vision Transformers from O(n<sup>2</sup>) to O(n) by introducing **Multi-Dconv Head Transposed Attention**.  It also introduced **Gated-Dconv Feed-Forward Network**. 

@manyana72 and I would like to add this model to Huggingface. 

cc: @NielsRogge 

### Open source status

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

### Provide useful links for the implementation

[Paper](https://arxiv.org/pdf/2111.09881.pdf), [Code Implementation](https://github.com/swz30/Restormer) and [pretrained model weights](https://github.com/swz30/Restormer/releases/tag/v1.0)
Hi @tushdon2, please let me know if and how can I contribute to this model.