The `sphinx-alt-text-validator` doesn't verify release notes and files other than `.py`

[arnaucasau]

We should extend the sphinx-alt-text-validator that each API use via VCS to check release notes and other files than just Python files.

https://github.com/Qiskit/documentation/blob/19ce99f62ac6862c43b6d7856ce72d97407dc85e/scripts/image-tester/sphinx_alt_text_validator/init.py#L28

The Qiskit SDK uses .yaml files for their release notes, and runtime uses .rst.

This is the output of the image checker if we run it in the https://github.com/Qiskit/qiskit/tree/main/releasenotes folder looking for yaml files:

Errors found in releasenotes/notes/1.0/add-annotated-to-drawers-8bcc3a069dd981ad.yaml:
- Error in line 19: .. plot::

Errors found in releasenotes/notes/1.3/add-twirl-circuit-ff4d4437190551bc.yaml:
- Error in line 9: .. plot::

Errors found in releasenotes/notes/1.3/remove_identity_equiv-9c627c8c35b2298a.yaml:
- Error in line 8: .. plot::
- Error in line 18: .. plot::

Errors found in releasenotes/notes/1.3/add-random-clifford-util-5358041208729988.yaml:
- Error in line 8: .. plot::

Errors found in releasenotes/notes/1.1/add-elide-swaps-b0a4c373c9af1efd.yaml:
- Error in line 11: .. plot::
- Error in line 25: .. plot::

Errors found in releasenotes/notes/1.1/star-prerouting-0998b59880c20cef.yaml:
- Error in line 8: .. plot:
- Error in line 20: .. plot:

Errors found in releasenotes/notes/1.1/remove-final-reset-488247c01c4e147d.yaml:
- Error in line 9: .. plot::
- Error in line 23: .. plot::

Errors found in releasenotes/notes/0.23/solovay-kitaev-transpiler-pass-bc256c2f3aac28c6.yaml:
- Error in line 30: .. plot::