Update react-refresh README

Author: gaearon

packages/react-refresh/README.md

@@ -1,7 +1,5 @@
 # react-refresh
 
-This is an experimental package for hot reloading.
+This package implements the wiring necessary to integrate Fast Refresh into bundlers. Fast Refresh is a feature that lets you edit React components in a running application without losing their state. It is similar to an old feature known as "hot reloading", but Fast Refresh is more reliable and officially supported by React.
 
-**Its API is not as stable as that of React, React Native, or React DOM, and does not follow the common versioning scheme.**
-
-**Use it at your own risk.**
+This package is primarily aimed at developers of bundler plugins. If you’re working on one, here is a [rough guide](https://github.com/facebook/react/issues/16604#issuecomment-528663101) for Fast Refresh integration using this package.