Add Windows specific compile instructions

[Trojaner]

CUDNN_PATH and CUDAToolkit_ROOT need to be set on Windows or it results in errors such as "cudnn.h not found"

[chengzeyi]

@Trojaner Hello, friend. If you have the nvidia-cudnn-cu12 pypi python package installed in your environment, the CUDNN_PATH should not be needed. Instead, the build system can find and use the header file from it.