Document naming convention for element-reflecting attributes

Context: w3c/aria#1878.

source

@@ -8230,6 +8230,10 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
    </li>
   </ul>
 
+  <p class="note"><span data-x="reflected IDL attribute">Reflected IDL attributes</span> of this
+  type are strongly encouraged to have their identifier end in "<code data-x="">Element</code>" for
+  consistency.</p>
+
   <p>If a <span>reflected IDL attribute</span> <var>attr</var> has the type <code
   data-x="">FrozenArray&lt;<var>T</var>&gt;?</code>, where <var>T</var> is either
   <code>Element</code> or an interface that inherits from <code>Element</code>, then:</p>
@@ -8402,6 +8406,10 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
    </li>
   </ul>
 
+  <p class="note"><span data-x="reflected IDL attribute">Reflected IDL attributes</span> of this
+  type are strongly encouraged to have their identifier end in "<code data-x="">Elements</code>" for
+  consistency.</p>
+
   </div>
 
   <h4>Collections</h4>