Add support for circle layer type.

[lazaa32]

trafficstars

From GL json specs - layer properties, there are these layer types:

type Required enum. One of fill, line, symbol, circle, heatmap, fill-extrusion, raster, hillshade, background, sky.

New maps Cadastre and Cadastre Satellite have some layers of circle type. Implementation should be able to read the props according to specs https://docs.mapbox.com/mapbox-gl-js/style-spec/layers/#circle