Live-mount config dir in docker-compose

Mount ./config into the bot container so config.yml / models.yml /
chat_modes.yml changes take effect with a simple restart instead of
a full image rebuild. Addresses #124.

docker-compose.yml

@@ -18,6 +18,9 @@ services:
     build:
       context: "."
       dockerfile: Dockerfile
+    volumes:
+      # live-mount config so edits apply on restart without rebuilding
+      - ./config:/code/config
     depends_on:
       - mongo