Add a linter to check the images' alt text (#718)

* Create linter and allowlist

* refactor linter and add it to CI

* refactor loop

* use VCS to install the linter

(cherry picked from commit 80b2a50)

tox.ini

@@ -19,6 +19,9 @@ commands =
   black qiskit_addon_cutting/ docs/ test/
 
 [testenv:lint]
+image-tester-commit = 7ae965ccf21c39e5170334ec7f4882756883860a
+deps = 
+  git+https://github.com/Qiskit/documentation.git@{[testenv:lint]image-tester-commit}\#egg=sphinx-alt-text-validator&subdirectory=scripts/image-tester
 extras =
   lint
 commands =
@@ -29,6 +32,7 @@ commands =
   mypy qiskit_addon_cutting/
   reno lint
   pylint -rn qiskit_addon_cutting/ test/
+  sphinx-alt-text-validator -f qiskit_addon_cutting -s qiskit_addon_cutting/instructions/move.py
   nbqa pylint -rn docs/
 
 [testenv:{,py-,py3-,py38-,py39-,py310-,py311-,py312-,py313-}notebook]