Add Troubleshooting for Being Stuck on Enabling Features for WSL

[hardy-ethan]

What
Today I saw someone who ran wsl --install and the installer got stuck on enabling Virtual Machine Platform. I haven't seen this issue before, and it occured after they attempted to reinstall WSL due to some issues they were having.

I asked them to try cancelling the command, enabling the feature manually with the "Turn Windows features on and off" dialog, and then try wsl --install command again. This worked.

It would be nice to mention this in the troubleshooting section.

Where
WSL -> Troubleshooting

Why
Students who run into this issue may be able to resolve it without needing additional outside assistance. The method to do the manual enable of the Virtual Machine Platform feature is already contained within the WSL page, but is part of Step 2 of the "Enable Virtualization" section. Since the content is already contained on the page, adding a separate point for it should be low workload.

References
I observed this happen in real-time, so I don't have a specific reference towards the issue. The step 2 I'm referring to in the Why section can be found here.

[awdeorio]

I was there in office hours for this so I can second @hardy-ethan suggestion.