Javascript docs: Accessibility and cosmetic changes to headings.

Closes #15915 by merging it.

docs/_includes/js/buttons.html

@@ -115,15 +115,15 @@
 {% endhighlight %}
 
   <h2 id="buttons-methods">Methods</h2>
-
-  <h4>$().button('toggle')</h4>
+  <h4><code>$().button('toggle')</code></h4>
   <p>Toggles push state. Gives the button the appearance that it has been activated.</p>
 
-  <h4>$().button('reset')</h4>
+  <h4><code>$().button('reset')</code></h4>
   <p>Resets button state - swaps text to original text.</p>
 
-  <h4>$().button(string)</h4>
+  <h4><code>$().button(string)</code></h4>
   <p>Swaps text to any data defined text state.</p>
+
 {% highlight html %}
 <button type="button" id="myStateButton" data-complete-text="finished!" class="btn btn-primary" autocomplete="off">
   ...