Fixes #2592: added info on how to translate framework messages at application level

docs/guide/i18n.md

@@ -393,6 +393,28 @@ Instead of using `fileMap` you can simply use convention of category mapping to
 
 > **Note**: For widgets you also can use i18n views, same rules as for controllers are applied to them too.
 
+
+### Translating framework messages
+
+Sometimes you want to correct default framework message translation for your application. In order to do so configure
+`i18n` component like the following:
+
+```php
+'components' => [
+    'i18n' => [
+        'translations' => [
+            'yii' => [
+                'class' => 'yii\i18n\PhpMessageSource',
+                'sourceLanguage' => 'en',
+                'basePath' => '/path/to/my/message/files'
+            ],
+        ],
+    ],
+],
+```
+
+Now you can place your adjusted translations to `/path/to/my/message/files`.
+
 Views
 -----