docs: enhance documentation with mailserver-admin configuration details #15

Job	Run time
sync (jeboehm/mailserver-virus)	5s
sync (jeboehm/mailserver-mta)	4s
sync (jeboehm/mailserver-ssl)	6s
sync (jeboehm/mailserver-mda)	7s
sync (jeboehm/mailserver-filter)	7s
sync (jeboehm/mailserver-db)	6s
sync (jeboehm/mailserver-unbound)	4s
sync (jeboehm/mailserver-web)	4s
	43s

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