Add missing comma

Author: fatosmorina

content/docs/reference-react.md

@@ -66,7 +66,7 @@ See the [React.Component API Reference](/docs/react-component.html) for a list o
 
 ### `React.PureComponent`
 
-`React.PureComponent` is exactly like [`React.Component`](#reactcomponent) but implements [`shouldComponentUpdate()`](/docs/react-component.html#shouldcomponentupdate) with a shallow prop and state comparison.
+`React.PureComponent` is exactly like [`React.Component`](#reactcomponent), but implements [`shouldComponentUpdate()`](/docs/react-component.html#shouldcomponentupdate) with a shallow prop and state comparison.
 
 If your React component's `render()` function renders the same result given the same props and state, you can use `React.PureComponent` for a performance boost in some cases.