[docs] Add supported operating systems, CPU vs GPU install

[Innixma]

In the installation instructions, it would be nice to detail the supported operating systems and any gotcha's that would complicate usage on any operating systems.

For example, in AutoGluon's installation documentation, there are separate tabs for each OS with OS specific details in case there are special requirements.

Additionally, it might be good to have separate install instructions for CPU and GPU machines. For CPU machines, you can get away with installing the CPU PyTorch version, which is a much smaller download (example in AutoGluon docs).