DEV: Add top level `<div>` (PR #12878)

We can use this for grids and footers and such, rather than having to rely on #main > div selectors.


I didn’t try this but I’m surprised it works when tagName is replaced by "" what is the component doing from className? it just ignores the fact that it can’t do anything with it, I thought it would error. Maybe it only error for bindings.

It’s not replaced in this case - the component is built either one way or the other, depending on features.

It’s not replaced in this case, the component class is built one way or the other depending on the features.

The title of this pull request changed from "DEV: Add discourse-root class to top level <div>" to "DEV: Add top level <div>