Update first-steps-with-celery.rst (#5093)

Add one-line instruction to run rabbitmq and redis on docker

docs/getting-started/first-steps-with-celery.rst

@@ -61,6 +61,12 @@ command:
 
     $ sudo apt-get install rabbitmq-server
 
+Or, if you want to run it on Docker execute this:
+
+.. code-block:: console
+
+    $ docker run -d -p 5462:5462 rabbitmq
+
 When the command completes, the broker will already be running in the background,
 ready to move messages for you: ``Starting rabbitmq-server: SUCCESS``.
 
@@ -80,6 +86,12 @@ the event of abrupt termination or power failures. Detailed information about us
 
 .. _`Redis`: https://redis.io/
 
+If you want to run it on Docker execute this:
+
+.. code-block:: console
+
+    $ docker run -d -p 6379:6379 redis
+
 Other brokers
 -------------