disclosure navigation Example: Add "Open in CodePen" button (pull #1651)

Co-authored-by: Valerie Young <[email protected]>

examples/disclosure/disclosure-navigation.html

@@ -57,7 +57,9 @@ <h2>Example Usage Options</h2>
   </label>
 
   <section>
-    <h2 id="ex_label">Example</h2>
+    <div class="example-header">
+      <h2 id="ex_label">Example</h2>
+    </div>
     <div role="separator" id="ex_start_sep" aria-labelledby="ex_start_sep ex_label" aria-label="Start of" ></div>
     <div id="ex1">
       <nav aria-label="Mythical University">
@@ -349,7 +351,7 @@ <h2 id="rps_label">Role, Property, State, and Tabindex Attributes</h2>
   <section>
     <h2>Javascript and CSS Source Code</h2>
     <!--  After the js and css files are named with the name of this example, change the href and text of the following 2 links to refer to the appropriate js and css files.  -->
-    <ul>
+    <ul id="css_js_files">
       <li>
         CSS:
         <a href="css/disclosure-navigation.css" type="tex/css">disclosure-navigation.css</a>
@@ -367,7 +369,7 @@ <h2 id="sc1_label">HTML Source Code</h2>
     <pre><code id="sc1"></code></pre>
     <div role="separator" id="sc1_end_sep" aria-labelledby="sc1_end_sep sc1_label" aria-label="End of" ></div>
     <script>
-      sourceCode.add('sc1', 'ex1');
+      sourceCode.add('sc1', 'ex1', 'ex_label', 'css_js_files');
       sourceCode.make();
     </script>
   </section>