Add accessibility (a11y) validation and features

[akonan]

Description

Ensure wiremd output follows accessibility best practices.

Features

Validation

• Check for alt text on images
• Ensure form labels are present
• Validate heading hierarchy
• Check color contrast ratios
• Verify keyboard navigation

Output Improvements

• Add ARIA labels where appropriate
• Semantic HTML tags
• Focus indicators
• Skip navigation links
• Screen reader friendly

CLI Flag

wiremd mockup.md --a11y-check
# Shows accessibility warnings

Priority

Medium

Labels

enhancement, accessibility, a11y