GitLab

Closes MAT-779
flag=none

Test Plan
1. Re-build canvas-rce and canvas JS bundles
2. Restart the Rails server
3. Navigate to an RCE and do something to trigger
   the A11y checker (example: insert an image with no
   alt text)
4. Verify the a11y checker shows a numbered notification
   badge over the checker button

Change-Id: I21952d497ee525f7ec2af8eee9a2cf8c2c3390f1
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/287608

Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Jake Oeding <jake.oeding@instructure.com>
QA-Review: Jake Oeding <jake.oeding@instructure.com>
Product-Review: David Lyons <lyons@instructure.com>