Add custom date (X-ABDATE)

[NeverWise]

Some "addressbook providers" like google and apple uses this extension.

apple for example uses this ones:

item2.X-ABDATE;type=pref:1604-09-04 item2.X-ABLabel:_$!<Anniversary>!$_

gmail contacts uses this ones:

item2.X-ABDATE:1604-09-04 item2.X-ABLabel:my date

I think it's a good idea let the user be able to add to a contact all the dates he needs.