Fix issue with multiple high severity warnings from mjml

[Saku75]

It seems mjml introduces 32 high severity warnings in the package.

I have looked into mjml and it seems to all come from a package called html-minifier.

I'm not sure if there is some possibility of removing mjml or an alternative solution.

It does seem mjml has multiple PRs open #2666 and #2858, but I'm not sure when we will see any updates on those.