DP doesnt offer that option per se but......you can just stop posting and allow your account to die on it's own. Or you can hit the report button, and then write why you want to delete your account. Maybe a mod will then delete it for you.
I don't believe there is a deletion option full stop. Just stop posting, because you may wish to return one day... stranger things have happened.
Already discussed recently (and answered by digitalpoint, the owner): https://forums.digitalpoint.com/threads/delete-account.2648857/ Change it to a redundant email address, set all the privacy options and never log in again is probably the closest you'll ever get.