Document that one must install cuda on windows to enjoy max performance for AI inference

[jcelerier]

https://developer.nvidia.com/cuda-downloads?target_os=Windows&target_arch=x86_64&target_version=11&target_type=exe_local

[jcelerier]

also cudnn: https://developer.nvidia.com/cudnn-downloads?target_os=Windows&target_arch=x86_64&target_version=10&target_type=exe_local