feat: export flat configs (fixes #342)

to use it, you can do:

```js
const eslintPluginRecommended = require('eslint-plugin-eslint-plugin/configs').recommended;

module.exports = [{
  ...eslintPluginRecommended,
}];

```

Author: aladdin-add

configs/index.js

@@ -0,0 +1,18 @@
+/**
+ * @fileoverview the configs for `eslint.config.js`
+ * @link https://eslint.org/docs/latest/use/configure/configuration-files-new
+ * @author 唯然<[email protected]>
+ */
+
+'use strict';
+
+const { configs, rules } = require('../lib/index.js');
+const configNames = Object.keys(configs);
+
+configNames.forEach((configName) => {
+  // the only difference is the `plugins` property must be an object
+  // TODO: we might better copy the config instead of mutating it, in case it's used by somewhere else
+  configs[configName].plugins = { 'eslint-plugin': { rules } };
+});
+
+module.exports = configs;

eslint.config.js

@@ -19,7 +19,7 @@ const js = require('@eslint/js');
 const { FlatCompat } = require('@eslint/eslintrc');
 const globals = require('globals');
 const markdown = require('eslint-plugin-markdown');
-const eslintPlugin = require('eslint-plugin-eslint-plugin');
+const eslintPluginConfig = require('eslint-plugin-eslint-plugin/configs').all;
 
 const compat = new FlatCompat({
   baseDirectory: __dirname,
@@ -63,8 +63,7 @@ module.exports = [
   {
     // Apply eslint-plugin rules to our own rules/tests (but not docs).
     files: ['lib/**/*.js', 'tests/**/*.js'],
-    plugins: { 'eslint-plugin': eslintPlugin },
-    ...eslintPlugin.configs.recommended,
+    ...eslintPluginConfig,
     rules: {
       'eslint-plugin/report-message-format': ['error', '^[^a-z].*.$'],
       'eslint-plugin/require-meta-docs-url': [

lib/index.js

@@ -47,7 +47,7 @@ module.exports.configs = Object.keys(configFilters).reduce(
   (configs, configName) => {
     return Object.assign(configs, {
       [configName]: {
-        // plugins: ['eslint-plugin'],
+        plugins: ['eslint-plugin'],
         rules: Object.fromEntries(
           Object.keys(allRules)
             .filter((ruleName) => configFilters[configName](allRules[ruleName]))

package.json

@@ -6,6 +6,7 @@
   "main": "./lib/index.js",
   "exports": {
     ".": "./lib/index.js",
+    "./configs": "./configs/index.js",
     "./package.json": "./package.json"
   },
   "license": "MIT",