PDF Settings - Confirmation on unsaved settings.

[jestonihpi]

Description
Gravity Forms provides a pop up for unsaved settings. I think we should also introduce this on our end.

Step To Reproduce
Steps to reproduce the behavior:

1. Go to 'PDF settings (Global or Form)'
2. Update any options
3. Refresh or Go to any page.
4. See error

Expected behavior
An alert box should pop up when you leave your unsaved settings.

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
This is to inline the general UX with Gravity Form.

[jakejackson1]

@debbieellis7 this would be a nice feature to add