Infrastructure: HTML validator paths are outdated

[howard-e]

Following the restructure of the repository, the current HTML validator being used is pointing to now absent paths. From package.json:

"vnu-jar": "java -jar node_modules/vnu-jar/build/dist/vnu.jar --filterfile .vnurc --no-langdetect --skip-non-html aria-practices.html index.html examples/"

aria-practices.html index.html examples/ should be content/. This change has been addressed in #2617. But new warnings have been introduced: #2617 (comment)

[howard-e]

Looking again at the log, it seems the only new (and non-zero blocking) error is:

example-usage-warning.html":8.9-8.11: error: Element “p” not allowed as child of element “summary” in this context.

Should this be updated or suppressed? cc @alflennik @mcking65

[alflennik]

@howard-e I looked into this an left a comment in the PR!