Adding TensorFlow port of LeViT
### Feature request

To add the TensorFlow port of the [LeViT](https://arxiv.org/abs/2104.01136) architecture. The architecture is currently present in the Transformers library in [PyTorch](https://github.com/huggingface/transformers/blob/main/src/transformers/models/levit/modeling_levit.py). 

### Motivation

[LeViT](https://arxiv.org/abs/2104.01136) is a family of architectures that optimize the trade-off between accuracy and efficiency in a high-speed regime. The TensorFlow port would be an addition to the hybrid architecutre families.

### Your contribution

I would like to make the contribution by building out the TensorFlow port.

Tagging: @amyeroberts who could assign me to the task of adding the TensorFlow port of the model.
This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.<|||||>I am still working on this.