Missing CSS declarations for Mapbox GL JS

[sdamerdji]

When I open inst/examples/shiny.R in the browser and inspect the page, there is this warning:

This page appears to be missing CSS declarations for Mapbox GL JS, which may cause the map to display incorrectly. Please ensure your page includes mapbox-gl.css, as described in https://www.mapbox.com/mapbox-gl-js/api/.

This warning also appears with the mapboxer package. Neither package displays a map when the height parameters has a value of 'auto' or '100%' in deckglOutput, which I suspect is related.