Spanish translation of asr.mdx and add_new_pipeline.mdx
# What does this PR do?

Translates `asr.mdx` and `add_new_pipeline.mdx` into Spanish. Also updates the `_toctree.yml` file accordingly. Includes minor typo corrections for the original versions of both files and the translated version of a file I had previously worked on.

Related to #15947

## 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?

@osanseviero @sgugger 
_The documentation is not available anymore as the PR was closed or merged._<|||||>I think I committed all the suggested changes, thanks @osanseviero !<|||||>Thanks again for your contribution!