Region Tile Pyramid Definition
An offline region definition is a geographic region defined by a style URL, geographic bounding box, zoom range, and device pixel ratio. Both `minZoom` and `maxZoom` must be ≥ 0, and `maxZoom` must be ≥ `minZoom`. The `maxZoom` may be ∞, in which case for each tile source, the region will include tiles from `minZoom` up to the maximum zoom level provided by that source. The `pixelRatio` must be ≥ 0 and should typically be 1.0 or 2.0.