Where a custom layer goes in the map's layer stack. It is a BeforeLayerConfig, or { layerID }
to go beneath a layer outside the map style, such as another layer of this module or one another
module added.
Remarks
If no layer on the map has the layerID, the layer goes on top, as MapLibre's addLayer does.
Where a custom layer goes in the map's layer stack. It is a BeforeLayerConfig, or
{ layerID }to go beneath a layer outside the map style, such as another layer of this module or one another module added.