Add Spanish translation of pr_checks.mdx
# What does this PR do?

Add the Spanish translation for `pr_checks.mdx` as part of the #15947 issue.
Changes include the Spanish version of the original document and the updated `_toctree.yml` file.


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests) Pull Request section?
- [x] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? _Task assignment [here](https://github.com/huggingface/transformers/issues/15947#issuecomment-1321245149)_.
- [x] Did you make sure to update the documentation with your changes? Here are the [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [x] Did you write any new necessary tests?
_The documentation is not available anymore as the PR was closed or merged._<|||||>Hi @osanseviero. Can you help review this PR, please? <|||||>Only minor typos were spotted during the first review. I already addressed them with my latest commit. 
@sgugger, if you agree, we can skip a second review from [osanseviero](https://github.com/osanseviero) and merge this PR. 

Thanks!