Added docs about new brokers.

Signed-off-by: Pavel Kirilin <win10@list.ru>

Author: s3rius

README.md

@@ -49,9 +49,17 @@ async def main():
 asyncio.run(main())
 ```
 
-## RedisBroker configuration
+## PubSubBroker and ListQueueBroker configuration
 
-RedisBroker parameters:
+We have two brokers with similar interfaces, but with different logic.
+The PubSubBroker uses redis' pubsub mechanism and is very powerful,
+but it executes every task on all workers, because PUBSUB broadcasts message
+to all subscribers.
+
+If you want your messages to be processed only once, please use ListQueueBroker.
+It uses redis' [LPUSH](https://redis.io/commands/lpush/) and [BRPOP](https://redis.io/commands/brpop/) commands to deal with messages.
+
+Brokers parameters:
 * `url` - url to redis.
 * `task_id_generator` - custom task_id genertaor.
 * `result_backend` - custom result backend.