feature: eslint-plugin-putout: export plugin (#232)

Author: coderaiser

packages/eslint-plugin-putout/README.md

@@ -17,7 +17,32 @@ npm i putout eslint eslint-plugin-putout -D
 
 ## Usage
 
-Update `eslint.config.js` with:
+### Plugin
+
+To use `putout` as ESLint plugin you can use in `eslint.config.js`
+
+```js
+import putout from 'eslint-plugin-putout';
+
+export default [
+    rules: {
+        'putout/putout': 'error',
+    },
+    plugins: {
+        putout,
+    },
+];
+```
+
+### Preset
+
+Also you can import one of predefined preset:
+
+- ✅ **recommended** - all rules enabled;
+- ✅ **safe** - dangerous rules disabled;
+- ✅ **safeAlign** - dangerous rules disabled + add whitespaces on empty lines;
+
+Here is how it can look like:
 
 ```js
 import {recommended} from 'eslint-plugin-putout';

packages/eslint-plugin-putout/lib/index.mjs

@@ -139,8 +139,4 @@ export const configs = {
     esm,
 };
 
-const {rules} = putout;
-
-export {
-    rules,
-};
+export default putout;

packages/eslint-plugin-putout/test/exports.mjs

@@ -7,3 +7,11 @@ test('eslint-plugin-putout: exports: rules', async (t) => {
     t.equal(rules, internal.rules);
     t.end();
 });
+
+test('eslint-plugin-putout: exports: default', async (t) => {
+    const result = await import('eslint-plugin-putout');
+    const internal = await import('../lib/plugin.mjs');
+    
+    t.equal(result.default, internal);
+    t.end();
+});