Feature/wgmv updates dql function documentation (#1084)

* Update dql_function.md (#1044)

* indentation

---------

Co-authored-by: Walter Vogel <walter@wgmv.de>

Author: npotier

Resources/doc/columns_configuration/annotations/dql_function.md

@@ -103,3 +103,15 @@ class Article {
 `sales.name:otherFunction:string` turns into `otherFunction(_sales.name, 'string')` in DQL
 
 `other:count:distinct` turns into `count(DISTINCT _a.other)` in DQL
+
+
+## Using GridBuilder
+```php
+<?php
+    ...
+    /* Example BlogPost has many Comments */
+    /** @var GridBuilder $builder */
+    $builder
+        ->setGroupBy('id') //important to setGroupBy otherwise the column will not aggregate
+        ->add('comments.id:count', 'text' ['title' => 'Number of Comments']);
+```