Use init to ensure the web container stops quicker

`sleep` discards a lot of signals, so we need the init system to do it for us

docker/dev/docker-compose.yml

@@ -4,6 +4,7 @@ services:
     build:
       context: ../../
       target: dev
+    init: true
     environment:
       - QUEUE_STORE_URL=redis://redis/0
       - DEBUG=true