add
Adds a new [style layer](https://docs.mapbox.com/mapbox-gl-js/style-spec/#layers).Note: This is an experimental API and is a subject to change.Whenever a new style is being parsed and currently used style has persistent layers,an engine will try to do following:- keep the persistent layer at its relative position- keep the source used by a persistent layer- keep images added through `addStyleImage` methodIn cases when a new style has the same layer, source or image resource, style's resources would beused instead and `MapLoadingError` event will be emitted.
Return
A string describing an error if the operation was not successful, or empty otherwise.
Parameters
A map of style layer properties.
If not empty, the new layer will be positioned according to `layer position` parameters.