update docker compose command (#350)

Co-authored-by: Thibaud Colas <thibaudcolas@gmail.com>

readme.md

@@ -91,9 +91,9 @@ Run the following commands:
 ```bash
 git clone https://github.com/wagtail/bakerydemo.git
 cd bakerydemo
-docker-compose up --build -d
-docker-compose run app /venv/bin/python manage.py load_initial_data
-docker-compose up
+docker compose up --build -d
+docker compose run app /venv/bin/python manage.py load_initial_data
+docker compose up
 ```
 
 The demo site will now be accessible at [http://localhost:8000/](http://localhost:8000/) and the Wagtail admin
@@ -108,7 +108,7 @@ Log into the admin with the credentials `admin / changeme`.
 To tail the logs from the Docker containers in realtime, run:
 
 ```bash
-docker-compose logs -f
+docker compose logs -f
 ```
 
 ## Setup with Virtualenv