doc: Update README.md

Author: jaywcjlove

core/README.md

@@ -19,7 +19,7 @@ A React component for displaying and editing javascript arrays and JSON objects.
 ## Features
 
 📚 Use Typescript to write, better code hints.  
-🎨 Support theme customization  
+🎨 Support theme customization & [`online editing`](https://uiwjs.github.io/react-json-view/#online-editing-theme) theme  
 🌒 Support dark/light mode  
 
 ## Quick Start
@@ -131,6 +131,8 @@ export default function Demo() {
 }
 ```
 
+## Online Editing Theme
+
 Online custom style example, please check in the [documentation website](https://uiwjs.github.io/react-json-view/)
 
 ```tsx mdx:preview