[Feature] Implement A11y page in devtool

[hannah-hyj]

internal link: go/devtool-a11y-userjourney

TODO:

• Add skeleton
• Accessibility override - brightness
• Accessibility override - text scale
• Accessibility override - bold text
• Accessibility override - screen reader debug mode
• Accessibility override - high contrast
• Semantics tree display
• Semantics tree scan - tap target
• Semantics tree scan - color contrast
• Semantics tree scan - semantics label