HTML dev docs
# What does this PR do?

This PR generates the *whole* docs inside the CI. So when the docs fail building, the CI is red instead of green.

You can see the generated html by `build_dev_documentation.yml` here: https://github.com/huggingface/doc-build-dev/tree/main/transformers/pr_15678

You can see the generated html by `build_documentation.yml` here: https://github.com/huggingface/doc-build/tree/main/transformers/doc-build-test

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).

## Changes to make

This is a multi-repo PR, for now relying on the `kit` branch of `doc-builder`: https://github.com/huggingface/doc-builder/pull/94. When everything's ready, the `master` branch should be used instead.

Remove `@kit`:

```
pip install git+https://github.com/huggingface/doc-builder@kit -U
```

```
ref: "kit"
```

## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

<!-- Your PR will be replied to more quickly if you can figure out the right person to tag with @

Documentation: @sgugger

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

 -->

_The documentation is not available anymore as the PR was closed or merged._