Add rounded documentation

docs/documentation/form/input.html

@@ -78,6 +78,10 @@ variables_keys:
 </div>
 {% endcapture %}
 
+{% capture rounded_example %}
+<input class="input is-rounded" type="text" placeholder="Rounded input">
+{% endcapture %}
+
 {% capture normal_example %}
 <div class="control">
   <input class="input" type="text" placeholder="Normal input">
@@ -299,6 +303,19 @@ variables_keys:
       </div>
     </div>
 
+    {% include anchor.html name="Styles" %}
+
+    {% include elements/new-tag.html version="0.6.2" %}
+
+    <div class="columns">
+      <div class="column is-half">
+        {{ rounded_example }}
+      </div>
+      <div class="column is-half">
+        {% highlight html %}{{ rounded_example }}{% endhighlight %}
+      </div>
+    </div>
+
     {% include anchor.html name="States" %}
 
     <h4 class="subtitle">Normal</h4>