build(docker): add Dockerfile, Docker Compose config, and update README

docker-compose.yml

@@ -0,0 +1,24 @@
+version: '3.8'
+
+services:
+  lavalink:
+    image: jagrosh/lavalink:latest
+    container_name: lavalink
+    ports:
+      - "2333:2333"
+    environment:
+      - LAVALINK_PASSWORD=${LAVALINK_PASSWORD}
+    volumes:
+      # Optional: mount custom configuration if needed
+      # - ./application.yml:/opt/Lavalink/application.yml
+
+  bot:
+    build: .
+    container_name: discord-music-bot
+    env_file:
+      - .env
+    environment:
+      - LAVALINK_HOST=lavalink
+      - LAVALINK_PORT=2333
+    depends_on:
+      - lavalink