docs: add dumi badge

Author: xrkffgg

docs/index.md

@@ -2,7 +2,7 @@
 
 React Performance First Form Component.
 
-[![NPM version][npm-image]][npm-url] [![build status][github-actions-image]][github-actions-url] [![Codecov][codecov-image]][codecov-url] [![npm download][download-image]][download-url]
+[![NPM version][npm-image]][npm-url] [![dumi](https://img.shields.io/badge/docs%20by-dumi-blue?style=flat-square)](https://github.com/umijs/dumi) [![build status][github-actions-image]][github-actions-url] [![Codecov][codecov-image]][codecov-url] [![npm download][download-image]][download-url]
 
 [npm-image]: http://img.shields.io/npm/v/rc-field-form.svg?style=flat-square
 [npm-url]: http://npmjs.org/package/rc-field-form