VirtualCity model is not defining any lights and is closed by a single-sided dome

The [VirtualCity](https://github.com/KhronosGroup/glTF-Sample-Assets/blob/main/Models/VirtualCity/glTF/VirtualCity.gltf) model will look completely black in a global illumination renderer because none of the materials define any emission and the city is enclosed by a single-sided dome geometry.

It _works_ when switching all materials to **unlit**.

The right way to implement self-illuminating objects (the surrounding dome, lit windows on the buildings) would have been to assign the textures currently used for the baseColorTexture to the emissiveTexture with an emissiveFactor of white (also or instead, depending on the intended surface material look).

Start with Models/VirtualCity/glTF/VirtualCity.gltf and inspect its materials, textures, and dome geometry. Verify the model in a global illumination renderer; done means the dome and lit windows contribute emission and the city is no longer completely black without switching all materials to unlit.

Written by the indexing model from the issue text.