Update docker-compose.yaml

Author: floryn08

game-servers/docker-compose.yaml

@@ -21,6 +21,7 @@ services:
       AUTOPAUSE_TIMEOUT_INIT: 150
       MAX_TICK_TIME: -1
       ENFORCE_WHITELIST: ${ENFORCE_WHITELIST}
+      EXISTING_WHITELIST_FILE: ${EXISTING_WHITELIST_FILE}
       VERSION: ${MINECRAFT_VERSION}
       TYPE: VANILLA
       VIEW_DISTANCE: ${MINECRAFT_VIEW_DISTANCE}