Documented the usage of refresh query hint if cache is used for translatable (#1021)

If query caching is enabled the TranslationWalker won't be used anymore once the query is cached. Therefore the `Query::HINT_REFRESH` won't be set automatically. This leads to the issue, that once a translateable entity is loaded a second query with another locale won't update the translateable properties in the entity.

Adding the `Query::HINT_REFRESH` manually to the query will fix the issue.

Author: stollr

doc/translatable.md

@@ -506,6 +506,11 @@ $query->setHint(
     \Gedmo\Translatable\TranslatableListener::HINT_FALLBACK,
     1 // fallback to default values in case if record is not translated
 );
+// refresh entities
+$query->setHint(
+    \Doctrine\ORM\Query::HINT_REFRESH,
+    true // update entity with correct locale if it was already loaded before
+);
 
 $articles = $query->getResult(); // object hydration
 ```