Add {appointment_date} to the New Appointment email title

[Valentina R]

It would be usefull to see the date and time of the appointment rather than the date of the order in the New Appointment email.

Requested here: https://bizzthemes.com/forums/topic/customizing-emails/

[Željan Topić]

Added {appointment_start} and {appointment_end} email shortcodes with update 3.8.6