Switch to html-validator.

This is a first try.

We could even use html-validator API. I had just started this.

Feel free to push to this branch if you have any ideas or want to use the API package which now that I think about it makes more sense.

TODO:

• See why ignore doesn't work It seems if verbose is used then everything is shown, even ignores
• Switch to html-validator
• See if there's a way to run multiple checks at the same time
• Handle error codes and return appropriately

Fixes #23171 (closed)