3D terrain on any style: terrain=on

Add terrain=on to a style URL, or terrain: true in the SDK, to draw any of the fifteen styles on 3D terrain, with an exaggeration from 0.1 to 5.

• GET /styles/{style}?terrain=on adds an unmap_terrain raster-dem source and a top-level terrain to the style, so MapLibre draws it in 3D when you tilt the map. Any style, flat ones included.
• exaggeration scales the relief from 0.1 to 5, default 1.
• In the SDK: createMap({ style: "winter", terrain: true, exaggeration: 1.5 }), and the same options on new Unmap(), styleUrl and unmapStyle.

AvailabilityAvailable once this gateway release and the next @unmap package release ship.