Add examples for both cases apache and fpm

.examples/dockerfiles/cron/apache/Dockerfile

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+FROM nextcloud:apache
+
+RUN apt-get update && apt-get install -y \
+  supervisor \
+  cron \
+  && rm -rf /var/lib/apt/lists/*
+
+RUN mkdir /var/log/supervisord /var/run/supervisord && \ 
+  echo "*/15 * * * * su - www-data -s /bin/bash -c \"php -f /var/www/html/cron.php\""| crontab -
+
+COPY supervisord.conf /etc/supervisor/supervisord.conf
+
+CMD ["/usr/bin/supervisord"]

.examples/dockerfiles/cron/apache/supervisord.conf

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+[supervisord]
+nodaemon=true
+logfile=/var/log/supervisord/supervisord.log
+pidfile=/var/run/supervisord/supervisord.pid
+childlogdir=/var/log/supervisord/
+logfile_maxbytes=50MB                           ; maximum size of logfile before rotation
+logfile_backups=10                              ; number of backed up logfiles
+loglevel=error
+
+[program:apache2]
+stdout_logfile=/dev/stdout
+stdout_logfile_maxbytes=0
+stderr_logfile=/dev/stderr
+stderr_logfile_maxbytes=0
+command=apache2-foreground
+
+[program:cron]
+stdout_logfile=/dev/stdout
+stdout_logfile_maxbytes=0
+stderr_logfile=/dev/stderr
+stderr_logfile_maxbytes=0
+command=cron -f

.examples/dockerfiles/imap/fpm/Dockerfile

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+FROM nextcloud:fpm
+
+RUN apt-get update \
+ && apt-get install -y libc-client-dev libkrb5-dev \
+ && rm -rf /var/lib/apt/lists/* \
+ && docker-php-ext-configure imap --with-kerberos --with-imap-ssl \
+ && docker-php-ext-install imap

.examples/dockerfiles/smb/fpm/Dockerfile

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+FROM nextcloud:fpm
+
+RUN apt-get update && apt-get install -y smbclient && rm -rf /var/lib/apt/lists/*