add mongo arbiter

mongo-arbiter/docker-compose.yml

@@ -0,0 +1,20 @@
+services:
+  mongo-arbiter:
+    # Use the same version as your data nodes!
+    image: mongo:7.0
+    container_name: mongo-arbiter
+    restart: always
+    network_mode: host
+    
+    # We pass the specific arbiter flags here
+    command: 
+      - mongod
+      - --replSet
+      - rs0
+      - --bind_ip_all
+      - --port
+      - "27017"
+      
+    volumes:
+      # Arbiters store very little data, but need a folder
+      - /docker/arbiter/data:/data/db