Add a GeoJSON polygon

Replicates the MapLibre example Add a GeoJSON polygon — the classic Maine polygon, authored with the region: sugar.

The complete document

# yaml-language-server: $schema=https://docs.maplibre-yaml.org/schema/latest/map.schema.json
# Gallery twin of https://maplibre.org/maplibre-gl-js/docs/examples/add-a-geojson-polygon/
# The `region:` sugar stands in for the hand-built Feature<Polygon>
# (coordinates are an array of linear rings, as in GeoJSON).
type: map
id: add-a-geojson-polygon
config:
  center: [-68.137343, 45.137451]
  zoom: 5
  mapStyle: "https://demotiles.maplibre.org/style.json"
layers:
  - id: maine
    type: fill
    source:
      type: geojson
      region:
        name: Maine
        coordinates:
          - - [-67.13734, 45.13745]
            - [-66.96466, 44.8097]
            - [-68.03252, 44.3252]
            - [-69.06, 43.98]
            - [-70.11617, 43.68405]
            - [-70.64573, 43.09008]
            - [-70.75102, 43.08003]
            - [-70.79761, 43.21973]
            - [-70.98176, 43.36789]
            - [-70.94416, 43.46633]
            - [-71.08482, 45.30524]
            - [-70.66002, 45.46022]
            - [-70.30495, 45.91479]
            - [-70.00014, 46.69317]
            - [-69.23708, 47.44777]
            - [-68.90478, 47.18479]
            - [-68.2343, 47.35462]
            - [-67.79035, 47.06624]
            - [-67.79141, 45.70258]
            - [-67.13734, 45.13745]
    paint:
      fill-color: "#088888"
      fill-opacity: 0.5

What to notice

region.coordinates is an array of linear rings, exactly as in GeoJSON Polygon — add a second ring to cut a hole.
The sugar node accepts only coordinates, name, and description; anything else is a parse error, so styling stays on the layer where it belongs.