Correct accessibility issues with dynamic content updates

Swagger UI has multiple buttons that dynamically change the content of the page. Users navigating the website with a screen reader might not know that anything changes, as there is no indication that it does, e.g.:

• no indication that there are validation errors when authorizing or that the authorization was successful (note: there is also no visual indication that the fields have validation errors)

• no indication that inputs become enabled when clicking on Try it out button

• no indication that there are validation errors or that the request was successful after clicking on Execute button in Try it out

• the fields with validation errors are not focused after clicking on Execute button

• no indication what was copied or that it was successful when clicking on Copy to clipboard button

We could possibly address it with: https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Guides/Live_regions

This task covers issues originally reported in:

• https://github.com/swagger-api/swagger-ui/issues/5248
• https://github.com/swagger-api/swagger-ui/issues/7350

Start by reviewing the authorization, Try it out, Execute, and Copy to clipboard flows described in the issue, along with the linked MDN live-regions guidance. Done means screen-reader users receive feedback for validation errors, successful actions, enabled inputs, and copied content, with invalid fields focused after Execute.