Multi window example should include example of how to bubble the close event on the main window to all children windows.

## Specific Demand

This is required because in certain circumstances you may launch a headless window (as seen in the overlay example) as a popup window. Closing the main window will actually do nothing on MacOS specifically if a headless window still exists from the same process.

## Implement Suggestion

Not quite sure on the exact fix but I assume simply calling close on all open windows prior to emitting the actual close event would be adequate.

Start by locating the multi-window and overlay examples and reading how they create and close headless or popup windows. Confirm the behavior on macOS, then make the example demonstrate closing child windows when the main window closes; done means no child window remains open after the main window's close event.

Written by the indexing model from the issue text.