Update docker command (#3600)

The newer versions of docker dont have the hyphenated command so update the documentation to reflect this.

.github/CONTRIBUTING.md

@@ -6,7 +6,7 @@
 
 For a simple local development environment running on PHP, you will need:
 ```
-cd ./dev && docker-compose up -d
+cd ./dev && docker compose up -d
 ```
 just navigate to [localhost:8000](http://localhost:8000/) to view the site.