doc: enable nitpicking for xref validation

Author: jorgepiloto

tox.ini

@@ -111,6 +111,7 @@ description = Check if documentation generates properly
 setenv =
     links: BUILDER = linkcheck
     html: BUILDER = html
+    BUILDER_OPTS = --color -v -j auto -W --keep-going -n
 passenv =
     ANSYSLMD_LICENSE_FILE
     LD_LIBRARY_PATH
@@ -126,7 +127,7 @@ extras =
     visualization
 commands =
     python -m build "{toxinidir}" --outdir "{toxinidir}/doc/source/_static/artifacts"
-    sphinx-build -d "{toxworkdir}/doc_doctree" doc/source "{toxinidir}/doc/_build/{env:BUILDER}" --color -v -b {env:BUILDER} -j auto -W --keep-going
+    sphinx-build -d "{toxworkdir}/doc_doctree" doc/source "{toxinidir}/doc/_build/{env:BUILDER}" {env:BUILDER_OPTS} -b {env:BUILDER}
 
 # The following environments are only for development purposes. Do not use in CI/CD.
 # Using these during a CI/CD can lead to unexpected issues due to a Docker-In-Docker