"Add External feed" focus stays on the toggle
"Add External feed" focus stays on the toggle

fixes COMMS-741

Test Plan
- Make the specifics of sections turns on
- Announcements go to the tray and toggle the menu
- Test the a11y focus of the component

Change-Id: I8a58cbf84fe791bd47bb3677a5e38aa4691b9b74
Reviewed-on: https://gerrit.instructure.com/139180
Reviewed-by: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>
Reviewed-by: Venk Natarajan <f9eab59b292314637a3c917fea4742741e36a19b@instructure.com>
Tested-by: Jenkins
QA-Review: Landon Gilbert-Bland <60d9ff23682c863d36b48b4c32c5ce5f434d29c0@instructure.com>
Product-Review: Aaron Kc Hsu <089edc94045de3d9f5f372fb17706d21afcc259f@instructure.com>

djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms