Making Facebook.com accessible to as many people as possible

This post details the technical implementation of enhanced accessibility features on the redesigned Facebook.com. Key contributions include: integrating linting with Flow typing and eslint-plugin-jsx-a11y to validate accessible markup and enforce ARIA property provision; implementing scalable font sizes using rems by transforming pixel values during the build process; utilizing React Context for contextual headings to ensure logical heading hierarchy; employing React Context for a centralized API to manage contextual keyboard commands; introducing a runtime analysis tool with a visual overlay to detect and report markup issues; developing reusable React components with built-in accessibility based on ARIA Practices Guide; creating React components for focus management, including FocusList for declarative keyboard navigation; and implementing a `useAccessibilityAlert` hook to generate screen reader announcements via `aria-live` regions.