[doc][skip ci] upd elastica related docs.

Author: makasim

docs/elastica-bundle/overview.md

@@ -0,0 +1,7 @@
+# Enqueue Elastica Bundle
+
+`EnqueueElasticaBundle` provides extra features for `FOSElasticaBundle` such as:
+
+* [Speed up populate command.](https://github.com/FriendsOfSymfony/FOSElasticaBundle/blob/master/Resources/doc/cookbook/speed-up-populate-command.md)
+
+[back to index](../index.md)

docs/elastica-bundle/populate-command-optimization.md

@@ -46,8 +46,8 @@
     - [Cli commands](magento/cli_commands.md)
 * [Yii](#yii)
     - [AMQP Interop driver](yii/amqp_driver.md)
+* [EnqueueElasticaBundle. Overview](elastica-bundle/overview.md)
 * [Use cases](#use-cases)
-    - [FOSElasticaBundle. Populate command optimizations](elastica-bundle/populate-command-optimization.md)
     - [Symfony. Async event dispatcher](async_event_dispatcher/quick_tour.md)
     - [Monolog. Send messages to message queue](monolog/send-messages-to-mq.md)
 * [Development](#development)