[css-display-3] Mention 'display: none'’s effect on interactivity per w…

…3c#2355 (comment)

css-display-3/Overview.bs

@@ -181,7 +181,8 @@ Box Layout Modes: the 'display' property</h2>
 		The 'display' property has no effect on an element’s semantics:
 		these are defined by the <a>document language</a> and <em>are not affected by CSS</em>.
 		Aside from the ''display/none'' value,
-		which also affects aural/speech output [[!CSS-SPEECH-1]],
+		which also affects the aural/speech output [[!CSS-SPEECH-1]]
+		and interactivity of an element and its descendants,
 		the 'display' property only affects visual layout:
 		its purpose is to allow designers freedom
 		to change the layout behavior of an element