Add CMake install rules

[Pandapip1]

I don't actually think this conflicts with #408. I've done some testing but definitely not enough for me to consider undrafting this just yet.

[richgel999]

This is awesome - and looks quite safe to merge. I'll do some testing and get it into our January 2026 release - maybe sooner.

[Pandapip1]

It looks like there's at least one issue in that the header files aren't found correctly (e.g. StereoKit needed a patch to go from #include <basisu_transcoder.h> to #include <basisu/basisu_transcoder.h> to build). This is probably wrong, and I'm still troubleshooting it but I'm working on getting everything for stardust-xr-server 0.45.1 building and working and then fixing issues like this. I think it's probably as easy as modifying like 321 but with the amount of changes I'm making I have to prioritize stuff.

[Pandapip1]

Fixed merge conflict and the headers are now installed to the correct location

[Pandapip1]

Looks like master's formatting is failing, hence the failed check