Add a link for the error boundaries codemod into the blog post (#10305)

* Add a link for the error boundaries codemod into the blog post

* Update 2017-07-26-error-handling-in-react-16.md

Author: koba04

docs/_posts/2017-07-26-error-handling-in-react-16.md

@@ -98,3 +98,5 @@ Error boundaries preserve the declarative nature of React, and behave as you wou
 ## Naming Changes from React 15
 
 React 15 included a very limited support for error boundaries under a different method name: `unstable_handleError`. This method no longer works, and you will need to change it to `componentDidCatch` in your code starting from the first 16 beta release.
+
+For this change, we’ve provided [a codemod](https://github.com/reactjs/react-codemod#error-boundaries) to automatically migrate your code.