doc: Update README.md

Author: jaywcjlove

core/README.md

@@ -41,6 +41,7 @@ npm install @uiw/react-codemirror --save
 | Name                                               | NPM Version                                                                                                                                                                                                                                                                                                                                                                           | Website                                                                                   |
 | :------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------- |
 | `@uiw/react-codemirror`                            | [![npm version](https://img.shields.io/npm/v/@uiw/react-codemirror.svg)](https://www.npmjs.com/package/@uiw/react-codemirror) [![NPM Downloads](https://img.shields.io/npm/dm/@uiw/react-codemirror.svg?style=flat)](https://www.npmjs.com/package/@uiw/react-codemirror)                                                                                                             | [`#preview`](https://uiwjs.github.io/react-codemirror/)                                   |
+| `react-codemirror-merge`                           | [![npm version](https://img.shields.io/npm/v/react-codemirror-merge.svg)](https://www.npmjs.com/package/react-codemirror-merge) [![NPM Downloads](https://img.shields.io/npm/dm/react-codemirror-merge.svg?style=flat)](https://www.npmjs.com/package/react-codemirror-merge)                                                                                                         | [`#preview`](https://uiwjs.github.io/react-codemirror/#/merge/document)                   |
 | `@uiw/codemirror-extensions-basic-setup`           | [![npm version](https://img.shields.io/npm/v/@uiw/codemirror-extensions-basic-setup.svg)](https://www.npmjs.com/package/@uiw/codemirror-extensions-basic-setup) [![NPM Downloads](https://img.shields.io/npm/dm/@uiw/codemirror-extensions-basic-setup.svg?style=flat)](https://www.npmjs.com/package/@uiw/codemirror-extensions-basic-setup)                                         | [`#preview`](https://uiwjs.github.io/react-codemirror/#/extensions/basic-setup)           |
 | `@uiw/codemirror-extensions-color`                 | [![npm version](https://img.shields.io/npm/v/@uiw/codemirror-extensions-color.svg)](https://www.npmjs.com/package/@uiw/codemirror-extensions-color) [![NPM Downloads](https://img.shields.io/npm/dm/@uiw/codemirror-extensions-color.svg?style=flat)](https://www.npmjs.com/package/@uiw/codemirror-extensions-color)                                                                 | [`#preview`](https://uiwjs.github.io/react-codemirror/#/extensions/color)                 |
 | `@uiw/codemirror-extensions-classname`             | [![npm version](https://img.shields.io/npm/v/@uiw/codemirror-extensions-classname.svg)](https://www.npmjs.com/package/@uiw/codemirror-extensions-classname) [![NPM Downloads](https://img.shields.io/npm/dm/@uiw/codemirror-extensions-classname.svg?style=flat)](https://www.npmjs.com/package/@uiw/codemirror-extensions-classname)                                                 | [`#preview`](https://uiwjs.github.io/react-codemirror/#/extensions/classname)             |