Document usage with local CUDA

[aaronmondal]

This is already possible, but we should probably document the workflow. I suspect that this is especially relevant for WSL2 users because the WSL CUDA driver tends to differ from the one we package in rules_ll#unfree.

Maybe we should add explicit checks that set certain rpath values for WSL as well?

[mimed95]

I can take a look at this.

[aaronmondal]

@mimed95 Thanks a lot! #61 Might be related.