docs: add flat config setup (#142)

README.md

@@ -16,7 +16,7 @@ Next, install `eslint-plugin-userscripts`:
 npm install eslint-plugin-userscripts --save-dev
 ```
 
-## Usage
+## Usage in legacy config
 
 Add `userscripts` to the plugins section of your `.eslintrc` configuration file:
 
@@ -26,6 +26,34 @@ Add `userscripts` to the plugins section of your `.eslintrc` configuration file:
 }
 ```
 
+## Usage in recent flat config
+
+Add an element to the config array in your `eslint.config.*` file :
+
+```js
+const userscripts = require('eslint-plugin-userscripts')
+
+module.exports = [
+  // other configs
+  {
+    files: ['*.user.js'],
+    plugins: {
+      'userscripts': {
+        rules: userscripts.rules,
+      },
+    },
+    rules: {
+      ...userscripts.configs.recommended.rules,
+    },
+    settings: {
+      userscriptVersions: {
+        violentmonkey: '*',
+      },
+    },
+  },
+]
+```
+
 ## Supported Rules
 
 | Rule                                                                             | Description                                                            | Recommended |