Relax ci.yml trigger for pull_request based on modified paths

[alvarobartt]

What's in this PR?

As of a previous PR at #5902, I've seen that the CI was automatically trigger on any file, in that case when modifying a Jupyter Notebook (.ipynb), which IMO could be skipped, as the modification on the Jupyter Notebook has no effect/impact on the ci.yml outcome. So this PR controls the paths that trigger the ci.yml to avoid wasting resources when not needed.

What's pending in this PR?

I would like to confirm whether this should affect both push and pull_request, since just modifications in those files won't change the ci.yml outcome, so maybe it's worth skipping it too in the push trigger.

[alvarobartt]

Also this could be extended to the rest of the GitHub Action yml files, so let me know whether you want me to have a look into it! 🤗

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint.

[mariosasko]

Maybe we can add

paths-ignore:
  - "docs/**"

to ci.yml and benchmarks.yml. The other supporting files are not modified often, so leaving them out is fine.