Add the integrator's guide Twenty-three pages on building, installing and embedding vgl: the core, host interfaces, defaults module, C++ wrapper, geodesy, the render interface and each backend, the atmosphere, the baker, the pack format, hosting packs and the reference server, the samples, troubleshooting, and attribution and licensing. The home page and sidebar list them. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Jeremiah van Oosten <jpvanoosten@hotmail.com>