refs TryGhost/Team#3122
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### <samp>🤖 Generated by Copilot at 87727d9</samp>
Added `data-testid` attributes to various elements in the announcement
bar settings feature to enable Playwright testing. Fixed a potential bug
with the `visibilitySettings` getter in the `visibility.js` component.
Added Playwright tests for the announcement bar settings feature in
`announcement-bar-settings.spec.js`.
