Reconsider lang attribute

Is your feature request related to a problem? Please describe. Lighthouse audits recommend adding a lang attribute to your HTML. With the goal of being minimal / zero config, it would be nice to set that attribute without writing a custom template or plugin.

Describe the solution you'd like A solution similar to #562

Describe alternatives you've considered Writing a custom template or plugin for it. The suggested solution of HTML Webpack Template has not been update in years and seems to have issues with Webpack 4?

Additional context I can see requesting arbitrary extensions could lead to feature bloat. I do think it's reasonable to use Lighthouse recommendations as the boundary to prevent feature bloat.