moved the js-enabled class to the html element. This counters FOUC.

I've moved the js-enabled class to the html tag for a few reasons.

- Stops FOUC by being enabled before the CSS is loaded. `html` is a more natural fit then `body` tag in this case.
- `js-disabled` class by default for css hook. In similar vain to `js-enabled`.

Maybe move in into existing `script` tag below?