Document how auto-hiding the cursor works, and how to disable this behavior

[zadjii-msft]

Inspired by microsoft/terminal#9676

Auto-hiding the cursor is standard on windows, yes, but conhost and the Terminal didn't do that (until recently). We should have a Troubleshooting section about this, and a guide on where to go in the Settings to re-enable that.

[mattwojo]

Added to the Troubleshooting doc: #518