Minor Documentation update - query cuda compute for docker .env (#6469)

docker/.env.example

@@ -1,6 +1,7 @@
 # by default the Dockerfile specifies these versions: 3.5;5.0;6.0;6.1;7.0;7.5;8.0;8.6+PTX
 # however for me to work i had to specify the exact version for my card ( 2060 ) it was 7.5
 # https://developer.nvidia.com/cuda-gpus you can find the version for your card here
+# Or for a programatic approach run `nvidia-smi --query-gpu=name,compute_cap --format=csv`
 TORCH_CUDA_ARCH_LIST=7.5
 # the port the webui binds to on the host
 HOST_PORT=7860