Add atm3 for migration

atm3/docker-compose.yml

@@ -0,0 +1,29 @@
+version: "3"
+services:
+  mc:
+    image: itzg/minecraft-server
+    tty: true
+    stdin_open: true
+    ports:
+      - "25565:25565"
+    env_file:
+      - stack.env
+    environment:
+      EULA: "TRUE"
+      TYPE: "AUTO_CURSEFORGE"
+      CF_SLUG: "all-the-mods-3"
+      CF_FILENAME_MATCHER: "6.1.1"
+      TZ: "America/Moncton"
+      ENABLE_ROLLING_LOGS: "true"
+      MAX_MEMORY: "6G"
+      VERSION: "1.12.2"
+      MOTD: "All The Mods 3"
+      DIFFICULTY: "normal"
+      SNOOPER_ENABLED: "false"
+      ALLOW_FLIGHT: "true"
+      SETUP_ONLY: "true"
+      USE_SIMD_FLAGS: "true"
+      ENABLE_RCON: "true"
+    volumes:
+      # attach the relative directory 'data' to the container's /data path
+      - /docker/appdata/atm3/data:/data