Confirmation of event registration email to Families/Workers

[bchiaruttini]

Automate email to user confirming when they register (or unregister) for an event. At minimum it would just confirm registration. Other enhancements include:
-Details of the specific event (name, date, time)
-Add to calendar function
-Ability to link to Stripe with opportunity for FAMILIES to donate to help defray the cost of these events.