Update README.md

Author: virtualvivek

src/core/docs/icons/README.md

@@ -6,7 +6,7 @@
 
 <img src="img/icon_single.png" width="180" />
 
-<p>icons are defined using prefix <code><b>icons10</b> .</code></p> 
+<p>icons are defined using prefix <code><b>icons10-</b></code></p> 
 
 ```html
 <i class="icons10-iconName"></i>