chore: update readme with formatting

Author: JounQin

README.md

@@ -29,6 +29,7 @@ It started as a fork of [`eslint-plugin-import`] using [`get-tsconfig`] to repla
   - [JS example](#js-example)
   - [Typescript example](#typescript-example)
   - [As a standalone ESLint plugin](#as-a-standalone-eslint-plugin)
+  - [Using `defineConfig`](#using-defineconfig)
 - [Configuration (legacy: `.eslintrc*`)](#configuration-legacy-eslintrc)
   - [TypeScript](#typescript)
 - [Rules](#rules)
@@ -162,7 +163,7 @@ export default [
 ]
 ```
 
-## Configuration (using `defineConfig`)
+### Using `defineConfig`
 
 ```js
 import { importX } from 'eslint-plugin-import-x'