[Doctest] Add new checks
# What does this PR do?
Checks to make sure that the examples in any `doc/en/...` are tested
Checks to make sure that any model or config examples are also nightly tested
_The documentation is not available anymore as the PR was closed or merged._<|||||>Will add all the files to the IGNORE_DOC_NON_TESTED<|||||>Mostly the intent is to make sure new models that are added to the library are doctested (while currently the reviewer has to make sure it is added, but we usually forget)<|||||>Looking at the new `check_pr_documentation_tests` that only checks files that are modified + in the `documentation_test.txt` , my initial goal of making sure that new models are tested is not attained. This PR will adress that, by adding a check to make sure that new model addition are adding the files to test them. cc @ydshieh <|||||>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.<|||||>Sure! Closing this.