QuantizedMeshLoader: Wrong documentation of skirtHeight

[amuedespacher]

When working on a map that uses quantized-mesh based terrain tiles, I realized that the documentation regarding skirtHeight on the QuantizedMeshLoader is incorrect.

Steps to reproduce:

• Load quantized-mesh based .terrain tiles with QuantizedMeshLoader and render it with e.g. deck.gl's TileLayer (and SimpleMeshLayer as sub-layer).
• Use the terrain.skirtHeight option (as per documentation) and set it to e.g. 100 (meter) to generate a skirt.

Actual result:

• Skirt is not generated
• Skirt is generated if skirtHeight is defined as quantized-mesh.skirtHeight instead, as can be read from the interface in https://github.com/visgl/loaders.gl/blob/88ca35c545a92d28350d073be74e1f540d42a806/modules/terrain/src/quantized-mesh-loader.ts#L13
• Therefore, documentation is not correct

Expected result

• Documentation is correct