Make the 3D View tool work with `<dialog>` elements

[captainbrosset]

The new <dialog> elements allow displaying web content in a top layer.

You can see a nice demo here: https://cdpn.io/pen/debug/ExQBMgq
And docs here: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dialog

The 3D View tool does not seem to support this notion of top layer. A top layer always appears above everything else in the DOM (and multiple top layers can co-exist and be stacked on top of each other).
The 3D View tool probably needs some special handling for this.

This was requested here: https://twitter.com/_baxuz/status/1540095041041059840
And, worth noting, the Chromium devtools is gaining support for top layer in the Elements panel too. See https://twitter.com/bramus/status/1540029969660887043

AB#40153985

[captainbrosset]

@joselea for info.