Adds documentation to add closer control to Notification component.
Adds documentation to add closer control to Notification component.

Signed-off-by: Son <5b5abc6173a3c5d3ea5064fbfd55fdb11b9aaceb@gmail.com>

karatechops/grommet-docs,grommet/grommet-docs,grommet/grommet-docs,karatechops/grommet-docs