add Confetti to storybook
add Confetti to storybook

refs LS-3318
flag=none

test plan:
  - yarn storybook
  - navigate to examples > shared > Confetti

qa risk: low

Change-Id: I3a36e51847adeced0264a4441c1444965e7b6187
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/297767
Reviewed-by: Robin Kuss <0b206b54367b2de0334896ea45826f0e3194bd35@instructure.com>
QA-Review: Robin Kuss <0b206b54367b2de0334896ea45826f0e3194bd35@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Product-Review: Davis Hyer <60fbffed049dcae9186e63e354cbc0b825bf5523@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms