[package:react-dom] updateREADME's Class Component to Function Component (#21829)
[package:react-dom] updateREADME's Class Component to Function Component (#21829)

* [package:react-dom] updateREADME's Class Component to Function Component

* Update README.md

Co-authored-by: Dan Abramov <ffbbe9cb1097e7ea6a3dedffde5b4fe769829acc@gmail.com>
facebook/react,facebook/react,facebook/react,yungsters/react,yungsters/react,facebook/react,facebook/react,yungsters/react,yungsters/react,facebook/react,camsong/react,yungsters/react,camsong/react,facebook/react,camsong/react,yungsters/react,camsong/react,yungsters/react,camsong/react,camsong/react,camsong/react