WCAG 4.1 Compatible

[dustinwhisman]

To make the extension as useful as possible, we should write CSS to test for as many regressions as possible according to WCAG guidelines, and let users toggle issues for guidelines on/off. If there are issues that could be detected reliably with JS, but not CSS, we can include those as well.

Includes

• Configuring the extension to allow users to toggle issues for this guideline on/off
• Writing CSS and/or JS to highlight issues related to this guideline (at least one issue, we can expand on this later)
• Ensuring that info/error/warning messages refer to this guideline