Email custom form submission to 'form-filler' and site owner

https://support.wix.com/en/article/corvid-tutorial-sending-an-email-on-form-submission

https://www.wix.com/corvid/forum/community-discussion/example-send-email-with-the-sendgrid-rest-interface

https://www.wix.com/corvid/forum/community-discussion/example-send-email-with-the-sendgrid-npm-interface