docker: Add redis section to docker-compose file

With a persistent volume.

docker/docker-compose.yml

@@ -8,3 +8,11 @@ services:
     ports:
       - 127.0.0.1:8080:8080
     restart: unless-stopped
+
+  # Uncomment if you want to use redis as cache
+  # redis:
+  #   image: redis:alpine
+  #   container_name: redis
+  #   restart: unless-stopped
+  #   volumes: 
+  #     - ./cache:/data