Differentiate between Guide component closing via Finish button or Close button

[nathanss]

What problem does this address?

I'm using the Guide component to show a 4 step guide on this PR.

button.focusing.mov

We would like to fire different events depending if the user closes the dialog through the Close button or the last step's finish button.

What is your proposed solution?

Either provide two different callbacks (onClose and onFinish) or provide a parameter on the onFinish callback to allow the component's consumer to know what was the button clicked.