What problem does this solve or what need does it fill?

This was a request by a user on discord to change the mouse cursor to the "not allowed" shape when the widget is disabled.

What solution would you like?

The solution is relatively trivial: just inserting the proper EntityCursor when the widget is disabled. There's already a function for each widget which modifies the widget's appearance based on whether it's disabled, we just need to include the cursor shape in the set of components affected.

What alternative(s) have you considered?

The alternative is to not do this. The 'not allowed' cursor isn't particularly pretty, and the visual appearance of disabled widgets is pretty clear.

Additional context

Because this task is so easy, and because of it's low priority, I had been saving it as a starter task for someone new to working on Bevy.