fix: make /var/log/crontab writeable for everyone.

Dockerfile

@@ -48,8 +48,10 @@ RUN apk update --quiet && \
         wget && \
     rm /var/cache/apk/* && \
     mkdir -p ${HOME_DIR}/jobs && \
+    mkdir -p /var/log/crontab && \
     rm -rf /etc/periodic /etc/crontabs/root && \
-    adduser -S docker -D
+    adduser -S docker -D && \
+    chmod u=rwx,go=rw /var/log/crontab
 
 USER docker