Added missing prop type

src/components/Button.jsx

@@ -9,7 +9,8 @@ class Button extends React.Component {
     onClick: PropTypes.func,
     style: PropTypes.object,
     className: PropTypes.string,
-    children: PropTypes.node
+    children: PropTypes.node,
+    disabled: PropTypes.bool,
   }
 
   render() {