Add issues to reading-order-items

Author: rachelandrew

css-display-4/Overview.bs

@@ -1151,6 +1151,12 @@ Reordering and Accessibility</h3>
 <h2 id='reading-order-items'>
 Reading Order: the 'reading-order-items' property</h2>
 
+ISSUE(9921): Should this property be 'reading-order' or 'reading-flow'?
+
+ISSUE(9922): Should this property also apply to tables?
+
+ISSUE(9923): A proposed alternative syntax.
+
 	<pre class='propdef'>
 	Name: reading-order-items
 	Value: normal | flex-visual | flex-flow | grid-rows | grid-columns | grid-order