[WIP] Add CAV-MAE model, initially cloned from VitMAE
Author: rationalism
Pull request: yes

# What does this PR do?

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Fixes https://github.com/huggingface/transformers/issues/28236


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Models:

- text models: @ArthurZucker and @younesbelkada
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- speech models: @sanchit-gandhi
- graph models: @clefourrier

Library:

- flax: @sanchit-gandhi
- generate: @gante
- pipelines: @Narsil
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- tokenizers: @ArthurZucker
- trainer: @muellerzr and @pacman100

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Comments:
Created an initial PR to add the CAV-MAE model by cloning the visual-audio multimodal model TVLT

Paper: https://arxiv.org/abs/2210.07839

Original model repo: https://github.com/YuanGongND/cav-mae

(haven't actually added the CAV-MAE code yet! this is just a scaffold)

Re-basing this on the ViTMAE model for ease of development (https://huggingface.co/docs/transformers/model_doc/vit_mae)

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.