Add PyTorch environment to custom-environments

[icoxfog417]

Is your feature request related to a problem? Please describe.
As a developer, I want to set up the environment to run the PyTorch quickly.

Describe the solution you'd like
Prepare the environment.yml for PyTorch. The dependencies should include packages to run most of the PyTorch tutorial.

• PyTorch and TorchVision is required
• Matplotlib is required

Describe alternatives you've considered
Install the PyTorch and the other dependencies by conda command.

Additional context
The CUDA version of Studio Lab is 11.2 (nvcc --version).

nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2021 NVIDIA Corporation
Built on Sun_Feb_14_21:12:58_PST_2021
Cuda compilation tools, release 11.2, V11.2.152
Build cuda_11.2.r11.2/compiler.29618528_0