Notification drawer demo

[mcarrano]

Follow on to patternfly/patternfly#3186 for adding a notification drawer demo in React. Should demonstrate behavior of the drawer integrated into a page including the notification badge with latest updates (#4323

cc @mcoker @tlabaj

[nicolethoen]

usage and behavior documentation: https://www.patternfly.org/v4/design-guidelines/usage-and-behavior/notification-drawer/