Add documentation

site/content/docs/05-accessibility-warnings.md

@@ -87,6 +87,18 @@ Enforce img alt attribute does not contain the word image, picture, or photo. Sc
 
 ---
 
+### `a11y-incorrect-aria-attribute-type`
+
+Enforce that only the correct type of value is used for aria attributes. For example, `aria-hidden`
+should only receive a boolean or `undefined`.
+
+```sv
+<!-- A11y: The value of 'aria-hidden' must be exactly one of true, false, or undefined -->
+<div aria-hidden="yes"/>
+```
+
+---
+
 ### `a11y-invalid-attribute`
 
 Enforce that attributes important for accessibility have a valid value. For example, `href` should not be empty, `'#'`, or `javascript:`.