Finished behavior guide [skip ci]

docs/guide/basic-configs.md

@@ -178,3 +178,27 @@ return [
     ],
 ];
 ```
+
+
+### Attaching behaviors from config
+
+One can attach a behavior to a component when configuring it with a configuration array. The syntax is like the
+following:
+
+```php
+return [
+    // ...
+    'components' => [
+        'myComponent' => [
+            // ...
+            'as tree' => [
+                'class' => 'Tree',
+                'root' => 0,
+            ],
+        ],
+    ],
+];
+```
+
+In the config above `as tree` stands for attaching a behavior named `tree`, and the array will be passed to [[\Yii::createObject()]]
+to create the behavior object.

framework/base/Behavior.php

@@ -46,8 +46,8 @@ class Behavior extends \yii\base\Object
      *
      * ~~~
      * [
-     *  Model::EVENT_BEFORE_VALIDATE => 'myBeforeValidate',
-     *  Model::EVENT_AFTER_VALIDATE => 'myAfterValidate',
+     *     Model::EVENT_BEFORE_VALIDATE => 'myBeforeValidate',
+     *     Model::EVENT_AFTER_VALIDATE => 'myAfterValidate',
      * ]
      * ~~~
      *