[Feat] MapboxOverlay z-index

[chunlampang]

Target Use Case

Since mapbox control has css z-index: 2; and MapboxOverlay is inside mapbox control container. Any deckgl content overlay on the mapbox will on top of the other mapbox components, e.g. mapbox popup will under deckgl Iconlayer. It is annoying to override the z-index to fix the issues.

Proposal

The MapboxOverlay canvas should place outside .mapboxgl-ctrl-top-left

[jessekrubin]

This is annoying!

Same problem with things like the ScaleControl from react-map-gl