Modal traps keydown event for esc key for the whole document

[jeffhem]

Detailed description

Other elements are not able to add keydown event for the escape key

The keydown event should not add to the document level and stop it from propagating

Steps to reproduce the issue

Add a event listener for the escape keydown event to any element in the document, and it's not response to the escape key

Additional information

the line of code doing that
https://github.com/IBM/carbon-components/blob/master/src/components/modal/modal.js#L139

[jeffhem]

Update: The event listener was attached to the document

[flannanl]

@asudoh Can you port this change to v9? I think we still have a long way to move to v10.