Add dependabot to manage auto-updates in Dockerfiles #53

Job	Run time
Build and push PHP 7.4	3m 53s
Build and push nginx	14s
Build and push PHP 8.0	4m 40s
Build and push nginx-proxy	19s
Build and push PHP 8.1	5m 1s
Build and push postfix	1m 23s
Build and push PHP 8.2	5m 3s
Build and push redis	10s
Build and push cron	15s
Build and push PHP 8.3	4m 54s
Build and push mailhog	16s
Build and push PHP stable	4m 6s
Build and push mariadb	14s
Build and push newrelic-daemon	18s
	30m 46s

Provide feedback