Export the definitions of [CEReactions] and [HTMLConstructor]

Per speced/bikeshed#677, this will allow
specs created with Bikeshed to automatically link to these (which is
primarily important for [CEReactions]).

source

@@ -9661,10 +9661,10 @@ interface <dfn>HTMLUnknownElement</dfn> : <span>HTMLElement</span> { };</pre>
   <h4 id="html-element-constructors">HTML element constructors</h4>
 
   <p>To support the <a href="#custom-elements">custom elements</a> feature, all HTML elements have
-  special constructor behavior. This is indicated via the <dfn
-  data-x="HTMLConstructor"><code>[HTMLConstructor]</code></dfn> IDL <span>extended attribute</span>.
-  It indicates that the interface object for the given interface will have a specific behavior when
-  called, as defined in detail below.</p>
+  special constructor behavior. This is indicated via the <dfn data-export=""
+  data-dfn-type="extended-attribute" data-x="HTMLConstructor"><code>[HTMLConstructor]</code></dfn>
+  IDL <span>extended attribute</span>. It indicates that the interface object for the given
+  interface will have a specific behavior when called, as defined in detail below.</p>
 
   <p>The <code data-x="HTMLConstructor">[HTMLConstructor]</code> extended attribute must take no
   arguments, and must not appear on anything other than an interface. It must appear only once on an
@@ -66924,7 +66924,7 @@ customElements.define("x-foo", class extends HTMLElement {
   <hr>
 
   <p>To ensure <span data-x="concept-custom-element-reaction">custom element reactions</span> are
-  triggered appropriately, we introduce the <dfn
+  triggered appropriately, we introduce the <dfn data-export="" data-dfn-type="extended-attribute"
   data-x="CEReactions"><code>[CEReactions]</code></dfn> IDL <span>extended attribute</span>. It
   indicates that the relevant algorithm is to be supplemented with additional steps in order to
   appropriately track and invoke <span data-x="concept-custom-element-reaction">custom element
@@ -92039,14 +92039,14 @@ dictionary <dfn>ImageBitmapOptions</dfn> {
      <code>DOMException</code> and abort these steps.</p></li>
 
      <li><p>If <var>image</var>'s media data has no <span>intrinsic dimensions</span> (e.g. it's a
-     vector graphic with no specified content size), and both or either of the <dfn><code 
+     vector graphic with no specified content size), and both or either of the <dfn><code
      data-x="dom-ImageBitmapOptions-resizeWidth">resizeWidth</code></dfn> and <dfn><code
      data-x="dom-ImageBitmapOptions-resizeHeight">resizeHeight</code></dfn> options are not specified,
-     then return a promise rejected with an <span>"<code>InvalidStateError</code>"</span> 
+     then return a promise rejected with an <span>"<code>InvalidStateError</code>"</span>
      <code>DOMException</code> and abort these steps.</p></li>
 
      <li><p>If <var>image</var>'s media data has no <span>intrinsic dimensions</span> (e.g. it's a vector
-     graphics with no specified content size), it should be rendered to a bitmap of the size 
+     graphics with no specified content size), it should be rendered to a bitmap of the size
      specified by the <span data-x="dom-ImageBitmapOptions-resizeWidth">resizeWidth</span> and the
      <span data-x="dom-ImageBitmapOptions-resizeHeight">resizeHeight</span> options.</p></li>