[css-display-3] Add note warning that 'display: contents' is fundamentally broken in browsers, breaks a11y access. w3c#3040

Author: fantasai

css-display-3/Overview.bs

@@ -590,6 +590,11 @@ Box Generation: the ''display/none'' and ''display/contents'' keywords</h3>
 			such as selector-matching, event handling,
 			and property <a>inheritance</a>,
 			are not affected.
+			<strong>As of writing, however,
+			<a href="https://github.com/w3c/csswg-drafts/issues/3040">this is not implemented correctly in major browsers</a>,
+			so using this feature on the Web must be done with care
+			as it can prevent accessibility tools
+			from accessing the element’s semantics.</strong>
 
 			This value computes to ''display: none'' on replaced elements
 			and other elements whose rendering is not entirely controlled by CSS;