doc: Fix the development setup documentation

`make docker-start` needs to be call before `make db-setup` since the
latter command doesn't start the database.

README.md

@@ -50,19 +50,25 @@ Install the dependencies:
 $ make install
 ```
 
+Start the development server:
+
+```console
+$ make docker-start
+```
+
 Setup the database:
 
 ```console
 $ make db-setup
 ```
 
-Start the development server:
+Create a user:
 
 ```console
-$ make docker-start
+$ ./docker/bin/console app:users:create --email=alix@example.com --password=secret
 ```
 
-And open [localhost:8000](http://localhost:8000).
+Open [localhost:8000](http://localhost:8000) and login with your user credentials.
 
 A note about the `make` commands: they might feel magic, but they are not!
 They are just shortcuts for common commands.