Proposal: native SketchUp (.skp) importer

Also posted as a discussion for open conversation: https://github.com/orgs/assimp/discussions/6836

Assimp has importers for dozens of formats but none for SketchUp's native .skp files — currently the only path in is exporting from SketchUp to a format Assimp already reads, which requires SketchUp itself.

OpenSKP is an MIT-licensed, from-scratch .skp reader/writer with a C++17 port (packages/cpp) — no Trimble SDK, cross-platform including Linux and WASM. Proposing a SkpImporter under code/AssetLib/Skp/ following Assimp::BaseImporter, mapping OpenSKP's scene output into aiScene/aiMesh/aiMaterial/aiNode, integrated with Assimp's IOSystem.

Happy to put together an RFC/PR if there's interest.