[SG-35195] Congratulate users on saving a form

Created by: gitstart-sourcegraph

Description

Screen reader should announce Saved Successfully on Saving changes to repository auto-indexing configuration

Problem description

Saving changes to repository auto-indexing configuration does not announce success. Failure is announced properly.

Expected behavior

Show a banner on successful save.

Refs

Sourcegraph Issue Gitstart Ticket

Test Plan

1. Change the value of codeIntelAutoIndexingEnabled to true on client/web/dev/utils/create-js-context.ts and run sg start web-standalone
2. Go through this link
3. On saving changes the screen reader announce Saved Successfully (if there is no any error)

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.