[Model] mT5 Cross-Lingual Model
# 🌟 New model addition

## Model description

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Multilingual T5 (mT5) is a massively multilingual pretrained text-to-text transformer model, trained following a similar recipe as T5.

Weights, code are available.

Github Repo: [mT5 Weights and Code](https://github.com/google-research/multilingual-t5)

Paper: [mT5: A massively multilingual pre-trained text-to-text transformer](https://arxiv.org/abs/2010.11934)

## Open source status

* [x] the model implementation is available: [Implementation](https://github.com/google-research/multilingual-t5)
* [x] the model weights are available: [checkpoints](https://github.com/google-research/multilingual-t5#released-model-checkpoints)
* [x] who are the authors: (@craffel, @adarob)

Will be a part of #6285<|||||>Hey, @sumanthd17 any update on this? <|||||>@julien-c thanks for your amazing nlp lib. 
When do you plan to support mT5 ?
When #6285 will be release ?
Cheers
Philippe <|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
