Collapsible: Added info and demo of collapsible coner styling to the docs.

Author: jaspermdegroot

docs/content/content-collapsible.html

@@ -157,6 +157,20 @@ <h3>Header swatch B</h3>
 			<p>I'm the collapsible content with a themed content block set to "d".</p>
 		</div>
 
+        <h2>Corner styling</h2>
+        
+        <p>To create an inset collapsible without rounded corners you can add the <code>data-corners="false"</code> attribute to the element.</p>
+
+		<code>		
+		&lt;div data-role=&quot;collapsible&quot; <strong>data-corners=&quot;false&quot;</strong> data-theme=&quot;b&quot; data-content-theme=&quot;d&quot;&gt;
+		</code>
+
+		<p>This code will create an inset collapsible without rounded corners:</p>
+
+		<div data-role="collapsible" data-corners="false" data-theme="b" data-content-theme="d">
+			<h3>I'm a header</h3>
+			<p>I'm the collapsible content.</p>
+		</div>
 
 
 		<h2>Nested Collapsibles</h2>
@@ -211,7 +225,6 @@ <h3>Section 4: Collapsed list</h3>
 		</div>
 
 
-		
 		<h2>Collapsible sets (accordions)</h2>
 		<p>It's possible to combine multiple collapsibles into a grouped set that acts like an <a href="content-collapsible-set.html">accordion widget</a>.</p>