Your extensions must meet the [Web Content Accessibility Guidelines](https://www.w3.org/WAI/standards-guidelines/wcag/)(WCAG). Meeting 100% conformance with WCAG 2.0 is hard work; meet the AA level of conformance at a minimum.
For more information on accessibility, check out the [WordPress accessibility quick start guide](https://make.wordpress.org/accessibility/handbook/best-practices/quick-start-guide/).