feat: add environment variable documentation and update configurations for socket port in Docker setup

docker-compose.yml

@@ -26,6 +26,7 @@ services:
       - DATABASE=${TELEGRAF_MONGODB_DATABASE:?"Database name is required"}
       - DSN=${TELEGRAF_MONGODB_DSN:?"DSN is required"}
       - HOSTNAME=${TELEGRAF_HOSTNAME:?"Hostname is required"}
+      - SOCKET_PORT=${SOCKET_PORT:?"Socket port is required"}
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8080"]
       interval: 5s