Add a docker-compose.yml file

Defines the services that we'll use while developing Tracks. So far,
this is just a separate database service.

docker-compose.yml

@@ -0,0 +1,19 @@
+version: '3'
+services:
+  db:
+    image: mysql:5.7
+    environment:
+      MYSQL_ALLOW_EMPTY_PASSWORD: '1'
+    volumes:
+      - "db-data:/var/lib/mysql"
+  web:
+    build: .
+    volumes:
+      - "${VOLUME:-:/app/workdir}"
+    ports:
+      - "3000:3000"
+    depends_on:
+      - db
+volumes:
+  db-data:
+