[UI] Consider WCAG guidelines

[edmondchuc]

This was raised in yesterday's WG meeting. The UI spec may want to include guidance or requirements related to accessibility, referencing WCAG.

[edmondchuc]

This was discussed in 2025-09-09 minutes - Accessibility Guidelines UI TF meeting.

Current plan:

• Include a section with common accessibility guidelines for key aspects of SHACL UI (input error, tooltip, etc).
• If time permits, expand with more detailed guidance for specific cases, such as constraint components. See this example with help text for sh:maxLength.