allow setting VERNEMQ_MAX_MESSAGE_SIZE

bin/vernemq.sh

@@ -105,6 +105,9 @@ EOF
         echo "vmq_webhooks.webhook4.no_payload = ${VERNEMQ_WEBHOOK_NO_PAYLOAD}" >> /etc/vernemq/vernemq.conf
     fi
 
+    if env | grep -q "VERNEMQ_MAX_MESSAGE_SIZE"; then
+        echo "max_message_size = ${VERNEMQ_MAX_MESSAGE_SIZE}" >> /etc/vernemq/vernemq.conf
+    fi
 
     echo "########## End ##########" >> /etc/vernemq/vernemq.conf
 fi