Update docker-compose.yml

add monitor mode env

examples/watchtower/docker-compose.yml

@@ -12,6 +12,7 @@ services:
       #- WATCHTOWER_NOTIFICATION_EMAIL_TO=john.doe@example.com
       #- WATCHTOWER_NOTIFICATION_EMAIL_SERVER=smtp.google.com
       #- WATCHTOWER_NOTIFICATIONS=email
+      #- WATCHTOWER_MONITOR_ONLY=true
       - WATCHTOWER_SCHEDULE=0 0 6 * * * # requires a go cron syntax of 6 space-separated fields; see https://containrrr.dev/watchtower/arguments/#scheduling
       - WATCHTOWER_CLEANUP=true # remove unused images afterwards
     image: containrrr/watchtower:latest