Refer people to "good first issue"

This tag is highlighted by GH. We can still tag them with difficulty.

README.md

@@ -67,9 +67,9 @@ Facebook has adopted a Code of Conduct that we expect project participants to ad
 
 Read our [contributing guide](https://reactjs.org/contributing/how-to-contribute.html) to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React.
 
-### Beginner Friendly Bugs
+### Good First Issues
 
-To help you get your feet wet and get you familiar with our contribution process, we have a list of [beginner friendly bugs](https://github.com/facebook/react/labels/Difficulty%3A%20beginner) that contain bugs which are fairly easy to fix. This is a great place to get started.
+To help you get your feet wet and get you familiar with our contribution process, we have a list of [good first issues](https://github.com/facebook/react/labels/good%20first%20issue) that contain bugs which have a relatively limited scope. This is a great place to get started.
 
 ### License