send notifications to list of subscribers for new projects

[JohnRDOrazio]

As suggested by Andrew DeBerry, it would be useful to be able to notify a list of people (Board of Directors, Ecclesial Advisory Council, Technical Advisory Council) of new projects that are submitted for incubation, for evaluation purposes.

[JohnRDOrazio]

Documentation added for a proposed implementation approach: docs/notification-email-lists.md

Summary: Each submission endpoint (submit-project, refer-community-project, refer-local-group) gets its own WordPress option (cdcf_notify_*) for the notification recipient, falling back to the admin email when unset. This is a one-line change per endpoint. The option value can point to a mailing list address (e.g. Google Group, Mailman) so Board members, Ecclesial Council, and Technical Council can subscribe to the relevant lists without needing WordPress accounts.

See the doc for full implementation details and mailing list provider recommendations.