fix(a11y): resolve accessibility issues in JsonViewer, SearchBox, and SelectOnClick

[ApurveKaranwal]

What/Why/How?

• What: Key interactive components in Redoc (JSON tree collapser buttons, Search Box clear icon, and SelectOnClick wrapper) were not keyboard-accessible or screen-reader friendly.
• Why: Users relying on assistive technologies or navigating with a keyboard alone could not focus on, activate, or understand the states (expanded/collapsed) of these components.
• How:
  • JSON Viewer: Updated the collapser button HTML generation to include aria-expanded and descriptive aria-label attributes. Handled keydown (Enter) triggers inside JsonViewer.tsx and called event.preventDefault() to prevent duplicate execution from the browser's synthetic click on <button> elements. Wrapped handlers in React.useCallback to satisfy ESLint warnings.
  • Search Box: Added tabIndex={0}, role="button", and aria-label="Clear search" to the clear search icon, alongside an onKeyDown handler listening for Enter/Space. Annotated search result box with role="menu", an dynamic results-found aria-label, and aria-live="polite" for the empty-results state.
  • SelectOnClick: Added tabIndex={0}, role="button", and aria-label="Select all text", enabling keyboard activation via Enter or Space.
  • Troubleshooting Docs: Updated the troubleshooting instructions in the README.md to help developers easily diagnose rendering or search issues.

Reference

Resolves accessibility gaps (WCAG 2.1 AA) in interactive components.

Tests

• Added Jest unit tests inside src/components/__tests__/JsonViewer.tsx to verify:
  • Collapser elements initialize with proper default aria-expanded and aria-label values.
  • Expanding and collapsing updates the ARIA attributes properly.
  • Pressing Enter correctly toggles the state of collapsers.
• Verified that the full test suite runs and passes (npm run unit).

##Fixes #2799

Screenshots (optional)

N/A (semantic markup changes)

Check yourself

• Code is linted
• Tested
• All new/updated code is covered with tests