Update Dockerfile

Dockerfile

@@ -1,6 +1,7 @@
 FROM alpine
 RUN apk --update add curl jq docker-cli
 RUN mkdir -p /opt/cron
+COPY crontab_letsencrypt.txt /opt/cron/crontab.txt
 COPY entrypoint.sh /entrypoint.sh
 COPY cron-re-read.sh /cron-re-read.sh
 COPY service /usr/local/bin/