feat(invoice): add Send invoice email action

Adds a Send button to the order action extension and a corresponding
"send" op to /api/orders/:orderId/invoice. Generates the invoice on
demand if missing, then sends via the configured SMTP.

shopify.app.toml

@@ -39,5 +39,4 @@ redirect_urls = [
 ]
 
 [build]
-include_config_on_deploy = true
 automatically_update_urls_on_dev = true